Those aren't scores; there are just three possible scores in chess: White wins, Black wins, and draw.

Those are evaluations of the chess engine; a score of +0.62 means the engine thinks White's position is better by 0.62 pawns. A negative score would mean Black is better. On professional level, a score of 1.5 pawns is in most positions decisive, i.e. enough to win the game. However, weak moves by the players will change the evaluation.

The maximum and minimum score depends on the chess engine you're using. If you play the game till checkmate, you will see that the scores will get larger (either more positive or more negative) until you see something like +#8 which means White can mate in 8 moves.


How do Kramnik and Topalov indicate a resignation when they play together?

If I remember correctly, they either just sign the scoresheet or stop the clock first and then sign the scoresheet to indicate that they resigned. There is no handshake, and they do not speak to each other since the WCC2006 controversy.

Here are two examples:
Candidates Tournament 2014, Rd. 13 (Kramnik-Topalov 1-0),
Norway Chess 2014, Rd. 6 (Topalov-Kramnik 1-0).

Addendum. Not asked in the original post, but one interesting (and related) question is also: How do Kramnik and Topalov agree to a draw? Signing the scoresheet or stopping the clock is not appropriate in this case, since the opponent might want to continue playing.

One obvious way is to repeat the position three times. If there is no threefold repetition on the horizon, the players can offer a draw through the arbiter (like in Sofia rules, used, for example, during the WCC 2010).


What to do when your opponent doesn't play along in the opening?

It sounds like you're a beginner. As such, you should be focusing more on tactics than openings.

First, just because they play a move that's not in your book, doesn't mean it's "wrong". It may be an older line that's not in modern opening books, or just not in the books you have.

That being said, to answer your question, it depends on the opening. In a slow, closed or positional openings, it's not likely to matter too much, when your opponent deviates from your book, just adjust your plans as necessary. If it's a gambit, or tactical opening, you should take some time to check to see if it's a blunder.


Which top player risks complicated positions?

As wrote in my answer to your other question: Jobava and Mamedyarov play very aggressively.

Ding Liren and Arkadij Naiditsch are another two top players who regularly risk absolute chaos on the board.


An aggressive counter for white vs Scandinavian Defense

I heard from everyone that only beginners do it for a reason but I can't exactly figure out why nobody else would use that defense.

It's not true that nobody but beginners use the Scandinavian - I use it, and my rating is in the 1700s.  The opening is, however, somewhat rare; I've only seen it about 4% of the time when I've played 1.e4 in tournament games. Some beginners perhaps like this opening because it gets their queen out early. But this is actually a bad thing for Black, not a good thing.

As White, one good idea is to make that queen your target. This game is the fastest I've lost playing the Scandinavian, and I lose when my opponent (rated 2042) traps my queen:

[FEN ""]
1.e4 d5 2.exd5 Qxd5 3.Nf3 Qa5 4.Be2 Nf6 5.O-O Bf5 6.d4 c6 7.c4 Nbd7 8.Nc3 e6 9.Bf4 Be7 10.a3 c5 11.Nb5 O-O 12.dxc5 a6 13.Bc7

And here's a game where a beginner (rated 535) tries the Scandinavian against me. Notice how, when possible, I attack his queen with moves that also develop my pieces.

[FEN ""]
1.e4 d5 2.exd5 Qxd5 3.Nc3 {I attack his queen. So far this is the mainline.} Qd4 {This is where we deviate from the mainline Scandinavian. This isn't the best square for his queen.} 4.Nf3 {I attack his queen again.} Qb6 5.Bc4 {I develop another piece. I don't attack his queen with Nd5 or Na4 because that wouldn't help me develop.} Nf6 6.O-O Qd6 {He moves his queen again. His plan is probably to trade off my f3 knight with Bg4 and Bxf3, and then play Ng4 to threaten Qxh2#.} 7.h3 {To prevent his plan. It wouldn't work, but Bg4 is annoying so I prevent it.} Nh5 {Moving his knight again and putting it on the edge of the board. That's usually not a good idea.} 8.Re1 {Activating my rook. It's not the strongest move I could have played. Ng5, attacking f7 and discovering an attack on his knight, was better.} Qg6 {Moving his queen yet again! We're on move 8, and he's moved his queen 5 times. His threat is Bxh3, and I can't play gxh3 because the pawn is pinned by the queen.} 9.Ne5 {Threatening his queen again. He can't play Bxh3 if his queen isn't safe. This also threatens his f7 pawn.} Qg5 {Still threatening Bxh3.} 10.d4 {A discovered attack on his queen. Perhaps I should have just played Bxf7+ now, but this also works.} Nf4 {Blocking the attack on his queen and threatening Qxg2#.} 11.Bxf4 {I have to do something about his checkmate threat.} Qxf4 {Eleven moves in, and his queen is his only piece that isn't on its starting square, while my army is just about fully developed. It's time for me to attack.} 12.Bxf7+ Kd8 13.Bd5 {Threatens Nf7+ forking his king and rook.} Qg5 {Trying to set up Bxh3 again, but it just makes my impending fork worse.} 14.Nf7+ {King-queen fork.} Ke8 15.Nxg5 h6 {From here I have a forced mate.} 16.Qh5+ Kd8 17.Nf7+ Kd7 18.Be6+ Kc6 19.Qc5# 1-0


There are many reasons why percentages are misleading. They can mean that the move is more often played when white is stronger than black, or in situations where a draw isn't what white wants, or there is a trap that many people fall into but that can be avoided, or lots of different reasons. Maybe it used to be considered good in the past until some novelty was found that refutes it, and then people stopped playing it.
For your game, what matters is how you will score playing it. That depends not on the results other people had with it in the past, but on how good your moves in the rest of the game are going to be.
So much more important than the winning percentage is how well you understand the idea behind the move. 5.Nge2 there is a bit odd since it doesn't pressure e5 and blocks the white bishop; but in return you keep options open with your f-pawn (you can still transpose to the Samisch, basically). Is that what you want? Do you think you can make the best of those pros and cons? Do you understand what black can do to make use of the cons, and are you ok with that?
That's the sort of thing you need to be asking instead of looking at percentages.
Although of course if they are extreme and you don't know why, that may be a hint that there is something you need to figure out.
Also, the problem with "is it better to play the less common because your opponent is less likely to be familiar with it" with a move that you are not familiar with, is that you are certain that you will be giving yourself that disadvantage, but there is still a chance that your opponent actually knows the move well. So only do that with sidelines you actually investigated a bit first.


What is Alpha Zero's Play Style? (Including its Openings and its Middlegame)

I want to know how I can play more like Alpha Zero. I think if we can
  see the main ideas that Alpha Zero uses (like fianchettoing his
  bishop) and put them into our own games, we could understand chess
  better and play better overall.

I don't think AlphaZero is any useful for teaching us chess. While I understand your enthusiasm, you learn more from your local master than a supercomputer.

  Here are some questions to spark your imagination! Would you describe
  Alpha Zero plays positionally of aggressively or anything in between?
  Does Alpha Zero prefer bishops or knights more? Does Alpha Zero use
  his f-pawn to attack the center or does it reject this idea? Does
  Alpha Zero Move his Queen to c2 often? I've seen it played in some of
  its games and I don't know the purpose why?

There is absolutely no way to infer from just 10 public games, but generally all modern engines prefer bishop a little better.

What we actually learn:

We haven't improved our chess playing strength from AlphaZero. What we learn is - machine learning works well with chess engine programming. Leela is a good example.

I've voted to close the question for too broad. If you can pinpoint your question to something more answerable, I'll modify my answer.


Chess tricks to fool opponents before game

Approach you opponent and ask him if he is good. He'll probably respond by saying that he is okay or pretty good. Then tell him how once you played someone who was really good and how you lost in ten moves. Also, it is preferable if you pretend to be 8 years old or younger. As you set up the board, make sure to set the board wrong. Place the knight where the bishop should go, and of course the queen should be misplaced as well. He'll correct you and you will pretend you didn't know. The most important thing is during the game. Make sure you seem undecided. Hover your hand around a random pawn and pretend like your thinking. Then hover around another pawn and do the same. Forget to press the clock a couple times. Do a couple illegal moves. I once had a person do exactly this. He pretend to be a child and oblivious to the rules of chess and I just played really fast and careless and lost. I lost because I didn't take my opponent seriously. Things are not always what they seem, so always keep your eyes open and don't underestimate your opponent. I'm assuming that the tournament you speak of isn't an official uscf because you didn't know how strong your opponents are(rating).


How does Black escape perpetual check here?

It seems that the black king can escape via a5/

[FEN "2k5/7p/p1Q3p1/3pP3/1r2qP2/1P4PK/P7/8 b - - 0 1"]

1...Kb8 2.Qd6+ Kb7 3.Qd7+ Kb6 4.Qd8+ Kb5 5.Qb8+ Ka5 {Kc5? 6. Qd6 Kd4?? 7.Qxb4} 6.Qc7+ Rb6 7.Qc5+ Rb5 8.Qc7+ Kb4 {and you go for the hills.}

edit: 5.a4+!, noticed by @jknappen, is problematic. The right solution is rather to bring the king to a7 before covering checks with ...Rb7, as in @InertialIgnorance 's answer which should become the accepted one.


Mobialia Chess Free includes an FICS interface; it supports premove and interfacing directly with the console.


An online dictionary of fairy chess pieces indexed by move

The best tool (online, but not a web tool) was (note past tense) the list you referred to. You need to learn about movement rules (the square root notation, or x/y notation) and base piece movements, but then you can just search for movement rules. (In a few cases, you may need to update it first ...)
It is almost certainly not up-to-date anymore, though, even though it's only two years old, and that makes it non-best by the standards you set. Keeping it up-to-date as well as complete ... is probably a kind of job that very few people would do without being paid for it.  Do it once, yes. Do it for five years, ... doubtful.
Some obvious issues:
Some fairy pieces (generally called Mimics, but that term is not in the glossary as far as I can find) get their movement rules from other pieces on the board (see Imitator and Joker for two.)
Some have movement rules that separate movement and attack. In, say, Rifle Chess they apply to all pieces, and may thus be seen as a general rule or condition, but individual rifle pieces have been observed. And many of the conditions described in the glossary can also be applied to individual pieces.
So for pure movement, this might  work. But it would require the user to know beforehand that the piece is a pure 'mover', and not a mimic or another type of piece, or the lack of search find would be misinterpreted. That user is probably advanced enough to be able to go to Emmerson's list, or to Encyclopedia of Chess Problems and the relevant articles (Combined Pieces, Hoppers, Leapers, etc.), or perhaps the Piececlopedia. Even so, the probability is fairly high that the piece won't be listed.
Fairy pieces are invented fairly rapidly: a 'piece finder' would not stay up-to-date more than about ... 6 months (guess)? Encyclopedia of Chess Problems warns that its list of combined pieces is far from complete.  So there's also a management problem: someone must keep all this updated.
That also leads to the question of being 'authoritative'. As there's no clearinghouse for naming of fairy pieces, this means keeping track of names and discussions in all chess problem literature, probably to the level where actual chess problem activities would be hurt.  And one person would probably lose interest after some time, so there must be an active and working hand-over system to ensure it stays alive.  (The chess problem community is not known for doing that kind of thing well.---personal note)
I suspect that if there is a tool such as you describe, it will be short-lived. Instead, let the would-be searcher after fairy pieces create his problems without bother about terminology, and then send them to an appropriate fairy chess journal, and the editors will help with the piece names.
(I think it was J. Berger or perhaps Ph. Klett who said that unorthodox chess should be regarded as a disease. You may be seeing one of the effects of such disease ... :-)
(Added: and it just strikes me that fairy chess boards, such as grid boards, or circular boards, or torus boards would probably also add to the complexity of identifying a mover piece.)
(Added again: I would not be surprised if there already was a sub-type of fairy chess problems, where the moves are listed, and the problem is to identify the fairy piece types  and their positions that make that solution 'correct'. Hm ... )


Pawn Promotion Endgame Problem-White to move and mate in 1

It's probably a trick problem with a promotion to a black knight.

Such promotions to the wrong colour are not allowed, and never were. In the official rules it is now specifically pointed out that the new piece has to have the same colour as the promoted pawn.

FIDE's laws of chess, Article 3.7 e:

  When a pawn reaches the rank furthest from its starting position it
  must be exchanged as part of the same move on the same square for a
  new queen, rook, bishop or knight of the same colour. The player’s
  choice is not restricted to pieces that have been captured previously.
  This exchange of a pawn for another piece is called ‘promotion’ and
  the effect of the new piece is immediate.


What projects have been undertaken to solve chess completely?

Endgame tablebases can be seen as such an effort, in that we started at few pieces and have increased the number. In 2012, 7 piece tablebases -from Moscow state university were generated, so chess is solved for positions of 7 or fewer pieces (including the kings).
The problem is, the 7 piece tablebases take about 140 TB in storage. 8 piece tablebases would take about 10 petabyte of storage, and a computer with 50 TB of ram (source) to keep hashes in memory to generate them in reasonable time (a few years?). I guess it would be doable these days if someone makes the millions of dollars available. 9 seems way out of reach.
So it will take a while before we get to 32.


How to make Lichess local analysis utilize more cpu and memory?

The menu for the analysis board has sliders for CPUs and memory (see screenshot below). Have you tried adjusting those? Maybe whether they actually work or not depends on which browser you are using. If they don't, I think this question would be best suited for the Lichess feedback forum, since it might be a bug.


Technique to win this same colored bishop endgame

The key here is zugzwang - White has an ideal defensive position at the moment, his king stops yours penetrating, his bishop covers the weak pawns on g4 and c4, and the pawn on a5 you can't easily get at is it is on a black square. BUT when white has to move he will either have to move his king (letting your king in), or move his bishop (leaving a pawn undefended) or move his a pawn (giving you an extra passed pawn)

So how can you take advantage of this? Well... if your bishop was on e6 and it was white's move he would be in zugzwang, and would either immediately drop a pawn (through a bishop or pawn move) or very soon afterwards (through a king move). Now note you can't just move your bishop straight to e6 as this would leave a position where you, not white, has the move. What you have to do is lose a move with the bishop - sometimes called triangulating with the bishop in reference to the similar idea with the King:

[Event ""]
[Site ""]
[Date "????.??.??"]
[Round ""]
[White ""]
[Black ""]
[Result "*"]
[FEN "8/1p6/5p2/P1p1k1p1/b1P1P1P1/4K3/4B3/8 b - - 0 1"]

1...Be8
    ( 1...Bd7?! 2.Bd1 Be6 3.Be2 {And white is OK for the moment
    } )
    ( 1...Kd6?? {Trying to get to the a pawn} 2.e5+ Kxe5 3.Bf3 Kd6 4.Bxb7 )
2.Bf1 Bd7
    {so losing a move}
3.Be2 Be6
    {Now white has the move and has to give you something}
4.Bf3
    ( 4.Kf3 Kd4 )
    ( 4.Kd3 Kf4 )
    ( 4.Kf2 {Stockfish's Choice} 4...Kd4
        ( 4...Kxe4?? {Be Careful!} 5.Bf3+ )
    5.Bf3 Kxc4 6.e5 fxe5 7.Bxb7 Kb5 8.a6 Kb6 )
4...Bxc4
    {and wins}
*

There's a free course at chessable (https://www.chessable.com/) called "Basic Endgames" which covers this, amongst many other things


I imagine Kevin's comment was somewhat hyperbolic. My local database has 1464 games with the position after 5.Qxd2, of which only 47% were drawn (although I imagine that percentage goes up as the players' strength increases). That is still enough to give the variation a reputation as drawish, but not enough to reliably predict that the game will end in a draw.

There are certainly variations that are more drawish than others, for concrete reasons. The best current example is the Berlin variation of the Spanish, where Black gets the queens off the board early and White has had trouble making anything of his positional advantages in the ensuing endgame.

In general the way that a game becomes more likely to have a decisive result is due to imbalances between the virtues of the two sides. The obvious example is a gambit, where one player has better development and the other player has an active pawn. In a situation with few imbalances (for example, the Exchange French or Exchange Slav), it is more difficult to play for a win.


Here is a solution to your question, since you changed the position, with the lines being on a board.

   [FEN "3r2k1/p3Rp1p/6p1/8/3nbP2/P1r3P1/P6P/2B1KR2 b - - 0 1"]

    1... Rxc1+ 2. Kd2 (2. Kf2 Rc2+ 3. Ke1 Nf3+ 4. Rxf3 Bxf3 5. Re8+ Rxe8+ 6. Kf1 Ree2 7. a4 Rc1#) 2... Rc2+ 3. Ke1 (3. Kd1 Nf3+ 4. Rd7 Rxd7#) 3... Nf3+ 4. Rxf3 Bxf3 5. Re8+ Rxe8+ 6. Kf1 Bg2+ 7. Kg1 Re1#


What "double moves" are sometimes considered legal?

Castling is the only legal chess move in which two pieces are moved. You can verify this by searching for "FIDE Laws of Chess" and reading "Article 3: The moves of the pieces" (I do not provide the URL here because unfortunately it frequently changes).


Carlsen - Ghaem, why does Black want to do e5?

With ...e5, Black:

Opens a diagonal for the c8-bishop, and
Fights for central control.

Both of these adhere to chess principles, so planning for ...e5 is a very natural thing for Black.


My understanding is that the dark squared bishop on g7 in this opening is a strong defensive piece and should be preserved there if possible.  White I know will typically try to trade off this bishop to enhance his own kingside attacking chances, by playing his dark squared bishop to e3 and supporting it with his queen on d2 so he can penetrate with this bishop to h6 to trade off black's g7 bishop.  Doing so will then weaken the dark squares around the black king, giving white better attacking chances there.


Why would a correspondence chess player be accused of using a computer?

The basis for such accusations is usually hurt pride.

That being said, if a player consistently plays moves proposed by a particular engine, you can be pretty sure that the engine is the source of these moves. But for such an assessment one game usually isn't enough and it is definitely possible to use an engine without leaving these tell-tale signs.


With best play, the position is unclear. If White plays 7. Kc3, then after 7...d4+!, Black gets a slight advantage. However, White can play 7. Qe1! and then the position is unclear.

    [FEN "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"]

    1. e4 e5 2. Nc3 Bc5 3. Na4 Bxf2+ 4. Kxf2 Qh4+ 5. Ke3 Qf4+ 6. Kd3 d5
    7. Kc3 (7. Qe1 $1 Nf6 8. c3 Bd7 9. Kc2 (9. Nc5 Bb5+ 10. Kc2 Qxf1)
    9... Bxa4+ 10. b3 Qxe4+ 11. Qxe4 Nxe4 12. bxa4 Nf2 13. Ba3 Nxh1 14. Nh3 f6
    15. Bd3 Ng3 16. hxg3 Nc6)
    7... d4+ $1 8. Kb3 Qf6 9. Nf3 (9. a3 Qc6 10. Ka2 Qxa4) 9... Bd7 10. a3 Na6
    11. Ka2 Bxa4 12. Bc4 Bd7 13. Rf1 Qe7 14. d3 f6


Caro-Kann advanced variation pawn sacrifice

The move 4. g4 is slightly dubious compared to the more solid option of 4. Nc3 (among Nc3), as it forces white to play 5. f3 if black opts for the mainline 4... Be4. Therefore I recommend this choice in general. It does, to an extent, weaken the idea of e6. However, 4... Bg6 is an option and a more common one at that.

The pawn sacrifice is actually quite common at the amateur level and can be an issue for the unprepared. Your most principled choice in your line is 5... fxe6 and it does work quite often well. After the mainline (if it can be so called) 6. Bd3, black should continue 6... Bxd3 7. Qxd3 Qd6 followed by the eventual fianchettoing of the bishop.

While this will not give you a simple win as black, it is clear that black's position is at least equal.


This variation is uncommon, but it's certainly not unheard of. I don't know of a particular name for it, and rather than get bogged down in the endlessly-analyzed lines, let's just take a quick, objective look at what this move accomplishes, and what it gives up.

Advantages

3.Bc4 aims, as you said, at the f7 pawn. If allowed to remain on the diagonal, this Bishop could provide pressure against the Black kingside in the midgame.
It develops the Bishop quickly, allowing White to castle kingside immediately if he so chooses.
It may avoid trading away the Bishop for Black's QN or QB like we see in the Canal-Sokolsky Attack (3.Bb5+) or other variations where White's KB lands on b5.
It grants White some additional influence over the light central squares weakened by Black's first two moves (c5 and e6).

Drawbacks

By developing to c4 so early, this move appears to invite Black to play ...e6, immediately limiting the Bishop's scope and possibly requiring a future relocation.
On c4, the Bishop is vulnerable to space-gaining queenside maneuvers via ...a6 and ...b5, or ...Nc6-a5.
This move does not provide any immediate threats, so Black is free to continue to choose a system as he pleases.

Ideas

Looking at these two lists, a picture begins to form of the themes for both sides.

White will likely try to hold onto this Bishop, to assist in his kingside operations. He will likely play 4.d3 to keep the position closed, and to cement his hold on the light central squares.

Meanwhile, Black may use the Bishop's placement as a convenient way to make his thematic land grabs on the queenside. Black is not compelled to respond in any particular way, though my database suggests that a Dragon-like setup with ...Nf6, ...Nc6, ...g6, ...Bg7 is slightly more popular in this line than the ...e6 variants.

[FEN "r1bq1rk1/pp2ppbp/2np1np1/2p5/4P3/1BPP1N2/PP3PPP/RNBQ1RK1 w - -"]
1. e4 c5 2. Nf3 d6 3. Bc4 Nf6 4. d3 Nc6 5. c3 g6 6. O-O Bg7 7. Bb3 O-O

Conclusion

This third move choice from White, while unusual, does not seem to be downright inferior. It suggests a tense, positional midgame, with each side operating on his better flank. Good luck!


What's so important about the h4 square in this endgame?

Your thoughts are correct.

In pawn endgames with play on both wings, it is often decisive for one side to be able to reduce his pawn majority to a 1 vs 0 situation ; reversively, he wants to ensure he keeps a pawn on the side where he has a pawn minority.

The idea is that the opponent king will be diverted by your eventual passer and take it (thus opening space for your breakthrough or counterplay on the other wing). If you have reduced your majority to a 1 vs 0 situation, there is nothing more for the opponent king to do. Otherwise, it would remain active and grab enough of your pawns on this wing to get a passer of his own.

I am familiar with this concept thanks to an excellent book by Glenn Flear. I haven't seen it in print anywhere else.

That's exactly what happens in your example. White gets a 4 vs 3 majority on the kingside. If he can reduce it by exchanging the h-pawns, he will sac his eventual extra f-pawn to distract the Black king and win on the other side (take Pc7, queen b-pawn).

However, if Black can retain the h-pawns (and if they are not too far north), the black king will be able, after taking the f-pawn, to also collect white h-pawn, and threaten to queen his own h-pawn.

That's why White needs to exchange the h-pawns early (or to ensure they stay far enough up the board for Black's counterplay to be too slow) with h2-h4 and hxg5.

See comments in this line:

8/2p2p2/7p/4k1p1/1P1pP2P/3K1PP1/8/8 w - - 0 1

1. hxg5 hxg5 2. b5 f6 3. f4+ gxf4 (3...Ke6 {loses trivially}) 4.gxf4 Kf4 5.Kd4 {Thanks to zugzwang, White can also exchange the 4 and f6, even if that's not necessary here} Kf3 6.e5 fxe5 7.Kxe5 {And the White King wins Pc7 and the game, while the Black King has nothing to attack anymore and is just out-of-play. Add wPh2/bPh4 and the evaluation changes !}


During the Revolutionary and Napoleonic Era, what was the rule for stalemate in France?

I can only cite Davidson, A short history of chess (Link), again. From chapter 8:

  [...] In Italy, however, from the very beginning, players could not accept stalemate as a victory for anybody. They argued that since no legal move was possible, the game simply stopped. Consequently in medieval Europe four different stalemate rules were simultaneously in effect, and travelling players had to agree in advance as to whether they were playing by the Spanish (victory for White), French (forfeited move for Black), British (victory for Black), or Italian (drawn game) rules. The Italian practice eventually spread throughout the Continent, partly because of the tremendous influence which Italy exercised on all European culture, partly because of the fame of Italian chess players, and partly because the rule seemed inherently logical. By the end of the eighteenth century every part of Europe (except Britain) had agreed that stalemate was a drawn game.

So according to this account, at least by the time of Napoleon stalemate was considered a draw in France.

ADDED: Even better, there is a contemporary source confirming that stalemate was considered a draw. Philidor, Analyse du jeu des échecs, 1777 edition (Link), rule XVI at the very end of the book confirms this:

  [...] En Angleterre, celui dont le roi est pat, gagne la partie; (b) en France, & dans plusieurs autres pays, le pat est un refait.


How are the "Classes" - A, B, or C, players defined?

The definitions you post are more of less correct though some levity has been inserted. The descriptions for the under-2400 ratings are consistent with the USCF.

IM and GM titles are not awarded by the USCF. They are awarded by FIDE and are based not upon rating but on achieving certain results at recognized tournaments.  That is, if one scores well enough at a FIDE tournament (based upon the competition), one earns an IM or GM "norm".  When one earns three norms, one is awarded the title.


No.

The main reason behind this train of thought was that they thought that blindfold chess may contribute to going crazy. They looked at Morphy and Pillsbury as their primary examples. Lasker, specifically, thought that blindfold chess made Pillsbury go mad, but we now know it was syphilis. Other than just plain incorrect assumptions like Lasker's, this is an incredibly small sample size no matter how you cut it, and we are talking about judging this on 90+-year-old "science", if you can call it that.

This not only does not make any sense in the modern day, but it has been debunked by at least USCF NM, and noted psychologist, Christopher Chabris from Harvard. The paper can be found here.

Blindfold chess is good for your chess vision, so feel free to practice it in moderation.

P.S. We have in more recent times, from 1992-2011, had the Melody Amber blindfold tournaments for the the top players in the world including Karpov, Kramnik, Anand, and Carlsen. If modern science even remotely believed that blindfold was bad for you, these guys would not have played.


Is one move considered as objectively better than another if they both lead to the same result?

Well, according to [Syzygy endgame tablebases](https://syzygy-tables.info/?fen=8/3k2PB/q7/8/4K3/8/8/8_w_-_-_0_1_, g8=R is a loss in 63 plies and g8=Q is a draw.  So g8=Q is definitely better.


What is the meaning of this chess opening theory table?

The two figures in the “Σ%” column are the number of games referenced in the database (so “Σ” should be understood in its mathematical meaning, “total” or “sum”) and the percentage of games won by White.


Example of a Karpov vs. Kasparov game with a controversial move

If you don't mind going a bit earlier, then it has to be 1972 Spassky–Fischer (mother of all World Championships) Game 1.
Fischer played 29...Bxh2? a move that few players would consider in light of the obvious 30.g3, trapping the bishop.
EDIT Later analysis (Speelman 1981) showed that the game is not lost (and can be drawn with extremely precise play), though the move was sub-optimal and the line becomes really sharp after 30. g3. The real blunder happened on move 37 with 37...Ke4 instead the optimal move again was just 37...a6. However, going by principles and elementary tactics 29...Bxh2? was an unnecessary move and chances are Fischer overlooked the fact that the trapped Bishop couldn't be saved.


This is a recognised opening. It's the Colle-Zukertort opening by transposition. The normal move-order for White is d4, e3, Bd3, Nf3, Nbd2 this is the Colle System, then b3, Bb2 to end up with this structure.
In the Colle, White breaks open the centre with the freeing move e3-e4 and gains piece play on the kingside which can turn into a king-side attack. White normally uses the e5-square for the knight in a Pillsbury/Stonewall style by following up with f2-f4. The bishop on b2 can come to life later on if Black tries to free himself with .. c5 or ... e5
With the g6-square weakened because of Black's ... h5, White has the plan of Ne5, f4, f5 threatening to exchange on e6 and now there's a hole on g6.
A quieter alternative is for White to play positionally with c2-c4 and after exchanging on d5 playing down the c-file.


In the vast majority of the cases, an ending of Q+R vs. Q should be winning.

However, some exceptions exist, for instance:

[FEN "6RK/7Q/5q2/8/8/8/8/3k4 w - - 0 1"]

      1.Qg7 Qh4+ 2.Qh7 Qf6+ 3.Rg7 Qd8+ 4.Qg8 Qh4+ 5.Rh7 Qf6+

In case you want to check whether your game was winning or not and how to win it, you can consult a tablebase, for example the free online tablebase of Shredder.


I am unsure what version of Stockfish you were using so I ran analysis 12 times; 4 seperate engines for each version of Stockfish.

Stockfish 10 vs ( Ethereal , Komodo, LC0 , Stockfish 12 )
Stockfish 11 vs ( Ethereal , Komodo, LC0 , Stockfish 12 )
Stockfish 12 vs ( Ethereal , Komodo, LC0 , Stockfish 12 )

Results were Stockfish (white) at the end of 20+ moves, was in a stronger position in all 9 instances. Based off this, I would suggest black is in a losing and in a irrecoverable position. There is the potential for a draw but it appears extremely unlikely.
The best variation / playout that I saw, that had the best end position for black, was Stockfish 12 vs Stockfish 12. +-3.03 / 41 so white is decisively better.
Issue with engine games in these sort of positions are the gameplay is boring. That being said, I have attached it for reference though.
[White "Stockfish 12"]
[Black "Stockfish 12"]
[FEN "4b3/4N1k1/3R3p/r7/8/P6P/5KP1/8 b - - 0 1"]

1... h5 2. Rd3 Kh6 3. Kg1 Kg7 4. Rc3 Kf7 5. Nc8 Kf6 6. Nd6 Bg6 7. Kh2 Ra4 8. Rf3+ Kg5 9. Nb5 Kh6 10. Nc7 Ra5 11. Ne6 Bf5 12. Re3 Bg6 13. Rc3 Bf7 14. Nf4 Kg5 15. Ne2 Ra4 16. Rf3 Bg6 17. Rg3+ Kh6 18. Rc3 Be4 19. Nf4 Ba8 20. Ne6 Ra5 21. Nc5 Bd5 22. Nd3 Ra4 23. Nb4 Be4 24. Re3

From my experience with engine games this is going to continue on for some time. Eventually the Black h pawn and Whites a pawns will go (will likely also involve trading out the bishops somewhere ) , white with the pawn advantage will promote.


You may be able to get some help from the following tips. Not all of them apply to everybody, so you must be able to think for yourself in a critical way, picking up what works best for you!

First, forget about centipawns! I would suggest to remove computer engine assistance completely if you want to improve your game. The reason is that, more often than not, checking positions with the engine is like copying in an exam. It helps you get the right answer, but does nothing to improve your knowledge. I am not saying that engines are useless for chess training, but I am saying that it's very difficult to distinguish when they should be used. This results in often doing more harm than good (it may help you judge a bad move as bad, but for the wrong reason!)
Then, you need to work on your tactics. Puzzles and studies are great, but (of course, unassisted) analysis of your own games also plays a role here. I really doubt you can find candidates and calculate accurately up to 10 moves deep. If you really could, you would be a top-tier Grandmaster. Work on finding out what mistakes you are doing without even realizing!
Once you have a decent tactical skill (which you probably are close to having given your ratings and games), you'll need to work on your endgames and middlegame strategy. Get a book that covers topics like piece activity, central control/counterplay, weak squares, good/bad bishops, open files and so on. Don't just stick to the general tips. Instead, analyze illustrative games in depth to study how those concepts translate into practical advantage. Try to find strategical themes in your own games as well.
Last, but not least, every time you make a move, it must have a purpose! If it doesn't, then it's a bad move! If the reason is more of an excuse than an actual reason, then it's a bad move, too! (See, for instance, the ...Bxf3 mentioned in DM's answer. What were the reasons/excuses behind that trade?)

PS: If you can afford one, get a professional coach! If they are expensive on your area, go online!


There definitely could be something to this.

My father, and a friend of mine, were air traffic controllers. They both told me that you generally want a smaller screen so you can see everything at once.

The friend was also a chess player, and we talked about how big you wanted the chess app or browser to display the board. It does seem to make sense that if it is smaller, that you can see everything, and thus, not miss something that is in your periphery vision.

I can very easily see that translating to a larger physical board that you see the pieces on an angle, if playing on a computer is your normal way of playing.

Of course, there may, or may not, be studies about this in similar situations; but I figure if the U.S. government trains their people about this, there is probably something to that even if I do not have the source material they base it on.


How to convert ChessBase format files to .pgn?

Well since the protocols creating cbv, cbf and cbh formats are not made publicly available, one will certainly not find any such conversion tool (i.e. unclear how they are encoded to reverse them to pgn).

Other reason maybe that the difference between all these formats is just due to an "incremental encoding" that is being used, which means that for it to be possible to go backward, to a pgn format, only the chessbase engine can do so!

Until a way around this is found, you can use playchess free program or easier the chessbase light (which is free), where using

choose file->new database and create pgn files

will allow you to obtain pgn formats again.


What activities should we set up in a chess club?

I run a chess club at my college. We have two meetings a week, 2 hours each, one run by myself and one run by someone else. We have a locker for our chess boards, mats and clocks and a meeting place in a lounge area that's not super busy but with decent foot traffic. We update our meeting times every academic quarter/semester to work around our classes and send out a survey to our email list to see when our members are available.

At our regular meetings, we just play chess, it's very casual. Usually blitz 5+0 or 10+0. We switch players every few games. Sometimes we play bughouse if there are enough willing participants. Sometimes we'll look at a position from a game, an opening, or a puzzle/tactic if people want to or have something interesting to talk about. If someone doesn't know how to play we teach them, we're not popular enough to be exclusive.

We have enough funding from the school to go to USCF tournaments in and around our city. Usually they're within walking distance, otherwise we carpool. We also sometimes host tournaments with $1 buy in.

People often say they would be interested in "workshops" to learn chess, but I don't want to host them.


Is e5 an usual move in positions like this in the King's Indian?

In KID positions like this with pawns on c5 and d6, knight on d7 I have never seen e5 without either Re8 or Qe8 first. e5 in this position is just a blunder,


Why is the Ruy Lopez such a common opening?

The Ruy Lopez is pretty much the epitome of opening principles.  White opens with the king pawn to claim the center, and black counters in the same way.  Then white develops a knight (knights before bishops!) to attack black's pawn.  Black defends the pawn with a knight.  Finally, white develops a bishop to b5 where it works in harmony with the knight to attack e5.  White prepares to castle at the same time.

So looking at the Ruy Lopez from that perspective, any other moves would violate some opening principle.  Obviously there are plenty of openings that are played, but the Spanish Game is one of the oldest and one of the best.


Resources on Italian Game, Two Knights Defense with 4. d3 h6 and quick ...g5

FM Andrey Terekhov's Two Knights Defense repertoire on Chessable uses this variation against 4.d3.
That repertoire deserves to be more widely known: it's one of the best on Chessable, the author updates it frequently, and it's free!
In the introductory text of 4.d3 h6 he notes:

In the beginning, this line has been mostly used as a surprise weapon, but in the past two years it developed its own body of theory. GM Alexey Kuzmin published a couple of articles summarizing the latest developments in this line in "ChessBase Magazine" (in 2018) and in Russian "64" (2019) .

So those are sources too.
And according to a ChessPub discussion, there are also two analyzed games in this line in Alexander Ipatov: Unconventional Approaches to Modern Chess Volume 1; Thinkers Publishing 2019, although I don't see it in that book's list of contents.


Is there some resource of non-tactical positions to practice analysing?

I looked at my library, and opened up a number of books. The old Dvoretsky books really do not do this much, but the "School of Future Champions" and "School of Chess Excellence" series do have many sections that just say "white (or black) to play", and nothing more.

Other Dvoretsky books that do that significantly are "Recognizing Your Opponent's Resources", which has 154 such examples. Also, "Chess Lessons" and "Maneuvering: The Art of Piece Play". That said, all of Dvoretsky's books are quite advanced, and you need to be above 2000 OTB, preferably 2200, to really benefit. His last book, "Chess Tests", was nothing but positions.

A couple of other tough books, but not as tough as Dvoretsky, are the classic "The Best Move" by Hort and Jansa, and "Test Your Chess Skills" by Sarhan Guliev and Logman Guliev. Again, both are a bit advanced, but still OK for a wider range of players.

My recommendation for most players are two outstanding series of books. The Yusupov series "Build up/Boost/Chess Evolution". There are 10 books in the series, and in each one, there is a lesson, and then a series of 12 test exercises for each lesson with just who is to move. The first four books are not simple, but they are accessible to players of a very wide range of OTB ratings. They get harder after that. This series is like having your own former top-10 GM as your teacher.

The other is the Jacob Aagaard series "Grandmaster preparation". There are 6 in this series, and there are many problems within each book. One of these books is even called "Grandmaster Preparation - Calculation".

Start with the first four Yusupov books, and go from there, is my recommendation.

P.S. The Yusupov books cover everything, from opening to tactics, to endgames, to positional play, as you specifically asked about.

P.P.S. NoseKnowsAll mentioned Silman below, and Silman posts a lot of articles he writes on chess.com. While not all are position-related, he does a lot about pawn structures, and other positions. You can find them here (click "More" at the bottom to see more of his articles to find the ones you want).


Adapted from here.

A gambit is said to be 'sound' if it is capable of resulting in an advantage against the opponent. There are three general criteria in which a gambit is often said to be sound:

Time gain: the player accepting the gambit must take time to obtain the sacrificed material and possibly must use more time to reorganize his pieces after the material is taken.
Generation of differential activity: often a player accepting a gambit will decentralize his pieces or pawns and his poorly placed pieces will allow the gambiteer to place his own pieces and pawns on squares that might otherwise have been inaccessible. In addition, bishops and rooks can become more active simply because the loss of pawns often gives rise to open files and diagonals.
Generation of positional weaknesses: finally, accepting a gambit may lead to a compromised pawn structure, holes or other positional weaknesses.

An example of a sound gambit is the Scotch Gambit:

[FEN ""]
1.e4 e5 2.Nf3 Nc6 3.d4 exd4 4.Bc4.

Here Black can force White to sacrifice a pawn speculatively with 4...Bb4+, but White gets very good compensation for one pawn after 5.c3 dxc3 6.bxc3, or for two pawns after 6.0-0 inviting 6...cxb2 7.Bxb2, due to the development advantage and attacking chances against the black king. As a result, Black is often advised not to try to hold on to the extra pawn.

An example of an unsound gambit is the so-called Halloween Gambit:

[fen ""]
1.e4 e5 2.Nf3 Nc6 3.Nc3 Nf6 4.Nxe5?! Nxe5 5.d4.

Here the investment (a knight for just one pawn) is too large for the moderate advantage of having a strong center.


Anti-cheating: should there be a limit to a number of toilet breaks per game per player?

No, there shouldn't and if you live to be 80 you will probably understand why.

A few years ago in a tournament where I was one of the arbiters a 16 year old boy was playing an old guy in his 80's in round 2, both of them were rated about 1950. There had recently been the case of the Bulgarian phone cheat who had consulted a phone hidden behind one of the toilets.

The 16 year old came up to me and said "Can I have a word with you outside?" It sounded very serious so I agreed. He then explained that his opponent was getting up regularly to go to the toilet even once doing it when it was his turn to move. The boy was worried his opponent was a phone cheat.

Had I been the boy's coach and not the arbiter I would have been able to explain the reasons. The old guy had just recently come out of hospital where he had had prostate surgery. The truth was he should really have been at home recovering with his feet up not playing chess but who is going to tell an 80 year-old how to live his life? In the previous round he had blundered his queen against a player rated about 1750. I would have told the boy to just keep playing good moves and the old guy was sure to blunder sooner or later. That is what happened in the game, by the way.

Of course as the arbiter I couldn't give him helpful information like that. Instead I told him I would check the toilets for mobile phones and keep an eye on the old guy for the rest of the round, which I did.

Note that the toilets are generally in the bounds of the playing venue but not in the playing area so going to the toilet when it is your turn is not allowed unless you get the permission of the arbiter. If you have a medical condition which makes this likely then you can speak to the arbiter before play to explain to the arbiter and get this permission.

If you are a woman then you can't have prostate problems but if you have children you may experience similar problems with needing to make regular visits to the toilet for some time after giving birth.

In short imposing limits on toilet breaks would be inhumane.


Is there some online chess board where you can teach a kid how to play?

The websites lichess.com and apronus.com are your best options to chose from. They both do the same thing, but I suggest you use apronus.com.
You can set up the board by yourself, send an invite link, and do other things just like you want.


1.Bxb2 and you're up a rook for a pawn.

1.Qxd1 Bxe5 and you're only up the exchange (rook vs bishop) for a pawn.


Sherlock Holmes vs Professor James Moriarty, A Game of Shadow-Chess Game Position Reconstruction

Here is my current solution. For convenience and resemblance to the Larsen-Petrosian game, I have assumed Sherlock Holmes is White.

    [FEN "1q3rk1/2p1p1b1/r1Ppn1p1/3R4/6B1/4BR2/PPn3PK/8 w - - 0 3"]

    3. Bxe6+ Kh7 (3... Rf7 4. Bxf7+ Kf8 5. Bxg6+ Bf6 6. Bh6+ Kg8 7. Rg3 Nd4 (7...
    e6 8. Rh5 Be5 9. Rxe5 dxe5 10. Be4+ Kh8 (10... Kf7 11. Rg7+ Kf8 (11... Kf6 12.
    g4 Qh8 13. g5#) 12. Bh7 Rxc6 13. Rg8+ Kf7 14. Rxb8) 11. Bg7+ Kg8 12. Bh6+) 8.
    Rh5 Ne2 9. Rg4 Be5+ 10. Rxe5 dxe5 11. Be4+ Kf7 12. Rg7+ Ke6 13. Rg6+ Kf7 14.
    Rg7+) 4. Rh3+ Bh6 5. Bxh6 Rf5 6. Rxf5 gxf5 7. Bf7! (7. Bxf5+? Kg8 8. Be6+ Kh7 9.
    Bf5+ (9. Bf7? Qc8 10. Rh4 Ra4! 11. g4 Qxg4 12. Rxg4 Rxg4)) 7... Qxb2 8.
    Bf8# (8. Bc1+ Kg7 9. Bxb2+ Kxf7)

Explanation:

After Sherlock plays 1. Bxe6, Moriarty is confident that the game is a draw by perpetual, so he plays 1...Kh7 immediately. Moriarty is unwilling to enter the complications of 1...Rf7, which also leads to a draw but gives a very complex position. After 1...Kh7, the forced sequence of moves arrives till 6...gxf5 when Moriarty expects Sherlock to take the pawn on f5 and give a perpetual. Instead, Sherlock plays 7. Bf7 and now Moriarty realizes it's over.

The variations show why 7. Bf7 leads to mate but 7. Bxf5+ leads only to a draw for Sherlock.


After 1...b6! Black can win a pawn. Whether that will be a winning endgame or not is a different matter, but I don't see a better plan for Black. So 1...b6 looks like the most reasonable way to pursue a win.

[FEN "3q2k1/pp1r1p1p/2p1p1p1/2Pr2P1/P2P1P2/4Q3/1P1R3P/3R2K1 b - - 0 1"]
[White "Comp"]
[Black "ALNS"]

1... b6 2. cxb6 (2. b4 a5 3. cxb6 axb4 4. Rc1 Qxb6 5. Rc4 b3 6. Rb2 Rxd4 7.
Rxd4 (7. Rxb3 Rd1+ 8. Kg2 R7d2+ 9. Kf3 Qd8) 7... Qxd4 8. Qxd4 Rxd4 9. Rxb3 Rxa4
10. Rf3 Kf8) 2... axb6 3. b4 (3. Kf1 c5 4. Qe4 cxd4) (3. Rc2 c5 4. Rc4
cxd4) 3... c5 4. bxc5 bxc5 5. h4 cxd4


Improving your worst piece is indeed generally a great thing to do if it's not a bad idea for tactical reasons. Some other standard general ways to improve your position:

Develop all of your pieces.
Occupy an open file with a rook (or queen). Bonus: double or triple your pieces on this file.
If you already have occupied an open file with a rook, move it to your seventh rank if possible.
Put your rook opposite the enemy queen.
Connect your rooks (get the other pieces out of the way so they're defending each other).
Castle.
Make sure you can't get mated on the back rank.
Make sure you don't have any undefended pieces (even if they're not attacked).
Defend an important pawn or square more than once (known as overprotection).
In the endgame, centralize your king.

Of course, tactical opportunities (for you or your opponent) trump these considerations, but all of these are general principles for improving your position in such a way that tactical opportunities are likely to turn out in your favor in the future. For example, putting your rook opposite the opponent's queen means that he has to worry about some situations in which the pieces in between move.


Can a chess engine tell you why a move is bad or good?

Sort of (but not really) - and it's actually getting harder for engines to do this for you.  To understand why, you have to understand how the evaluation goes.  Engines typically can make snap evaluations on a given position, giving it a raw point value.  Then, whatever the position is, they play forward, trying to find the line forward that optimizes that score for both sides.

It's important to understand, that '2.0' or '1.4' score aren't the evaluation/score for the current position.  Instead, it's the evaluation N moves down the line, with each side playing the best move the engine found.  This is why the "Current evaluation score" jumps around while the computer is thinking.  It's not that the 'score' for a position changed - it's just that it found a different line moving forward that ended up in a different position (which had a different score.)

In the past, engines sucked.  Not just because of sub-optimal algorithms, but because of very slow hardware - if you think compounding interest is powerful, it's nothing compared to Moore's Law.  So computers back then were just looking a few moves into the future.  Which made it relatively easy for a human to follow the logic - your score went down because you're losing your knight the next turn.

But now?  If your score went from '2.0' to '-0.3', it's possible it's because, due to some unavoidable tactics over the next 7 moves, that you'll have to give up the exchange in order to avoid losing your queen or getting checkmated.  But it's hard to show the leap from "Here's the position now" and "Well, I evaluated 20 billion positions going forward, and trust me when I say that you sacrificing the rook for their bishop was the best you could hope for."


Is this position a forced win for Black after move 14?

The best move would have been 16. Rxe5, which entirely eliminates the mate threat, leaving white with a winning advantage.

r6r/ppNk1p1p/3p2p1/2p1R3/2P3bq/3Q4/PP3PPP/R1B3K1 b - - 0 16

Here, if black takes the white knight (16. ... Kxc7), 17. Bg5 wins the queen as Qh5 is met with Bd8+.


What is the TimeControl format for FIDE tournament?

but it seems the increment is not allowed for the first period

As far as I can see from the standard it is allowed in the first period only if there is only one period. Specifically it is allowed only in the last period.

  •The fifth TimeControl field kind is used for an "incremental" control
  period. It should only be used for the last descriptor in a
  TimeControl tag value and is usually the only descriptor in the value.
  The format consists of two positive integers separated by a plus sign
  ("+") character. The first integer gives the minimum number of seconds
  allocated for the period and the second integer gives the number of
  extra seconds added after each move is made. So, an incremental time
  control of 90 minutes plus one extra minute per move would be given by
  "4500+60" in the TimeControl tag value

The only suggestion is the standard one regarding these questions about PGN which is to put the information in a comment field. The standard is old and no longer maintained as far as I know.


How to store moves for a magic bitboard system?

It sounds like you have all the tools to do the job, you just need to put it all together.  And yes, you can use the magic numbers you found.
When your engine initializes (or any time before you begin the search, really) you'll need to pre-compute the move board for every possible permutation of blockers you might encounter during the search.
Initialization
for each square...
  ROOK_MASKS[square] = //rook attacks on an empty board

  int bits = bitCount(ROOK_MASKS[square]);
  ROOK_SHIFTS[square] = 64 - bits;

  int permutations = 1 << bits
  for each permutation (p)...
    int index = (ROOK_MAGICs[square] * ROOK_MASKS[square]) >>> ROOK_SHIFTS[square];
    long blockers = //the pth permutation of ROOK_MASKS[square]
    ROOK_ATTACKS[square][index] = //rook attacks with blockers

Then when it comes time to generate moves you need to perform a similar operation using the pieces actually on the board
Move Generation
  long blockers = ROOK_MASKS[square] & //all the pieces on the board
  int index = (ROOK_MAGICS[square] * blockers) >>> ROOK_SHIFTS[square];
  return ROOK_ATTACKS[square][index];


Carlsen-Anand, game 8 -> how can Black repel 25.Rc7?

It is definitely worth considering, and probably an equally good move, but unfortunately it only leads to a similar simplification of the position (rather quickly), so Rc7 wouldn't really give an edge because black is well prepared to face it, as Ne7 prepares it. Either black replies by 25.Rc7 Bc6, locking the rook in to force the exchange, e.g. 26.Nd4 is just met by Rc8. Alternatively black can just exchange on f3, and play for minor activity himself, e.g. Nd5 or Rd2 after gxf3. (not necessarily a desired double-pawn structure for white either). Instead Anand went for activating his other rook and double his c-file, but black is just prepared enough to challenge it with an immediate Rc8, so long story short, the position just doesn't have much left in it to play for.

[White "Anand, Vishwanathan"]
[Black "Carlsen, Magnus"]
[Event "WCC 2014"]
[fen ""]
[Result "1/2-1/2"]

1.d4 Nf6 2.c4 e6 3.Nf3 d5 4.Nc3 Be7 5.Bf4 O-O 6.e3 c5 7.dxc5 Bxc5 8.a3 Nc6 9.Qc2 Re8 10.Bg5 Be7 11.Rd1 Qa5 12.Bd3 h6 13.Bh4 dxc4 14.Bxc4 a6 15.O-O b5 16.Ba2 Bb7 17.Bb1 Rad8 18.Bxf6 Bxf6 19.Ne4 Be7 20.Nc5 Bxc5 21.Qxc5 b4 22.Rc1 bxa3 23.bxa3 Qxc5 24.Rxc5 Ne7 25.Rc7 Bc6 (25...Bxf3 26.gxf3 Rc8 27.Rfc1 Red8 28.Be4 a5 29.f4 Kf8) 26.Nd4 Rc8 27.Rxc8 Rxc8 (27.Ra7 Bd5) 28.Rc1 Bb7


The FICS online game database has move times, however those are mostly blitz and rapid time controls, so the time used will not be indicative of tournament play.

Note that you can filter the database to only allow for your desired time controls, as well as rating range.


Would bishops be stronger or weaker on the same coloured squares?

And the correct answer, as always, is: "it depends on the position" :-)
OK, assume that you start with Bb1/Nc1. Lichess says +0.1. But this is the sum of...

the N generally standing a bit ugly on c1/f1, from my positional feeling
the B doing some concrete attacking (Stockfish unsubtly starts with c3)
other random concrete aspects
the question you asked: What is the isolated effect?

The isolated effect, of course, is that you are a whole piece up on all white squares, but down on black squares. GM Bangiev would rejoice: Adapt your strategy to be playing your dominance on white. (If that is possible.) For example, Bc4+Ng5 against short castling is completely useless. Fire it up with an additional Bb3 and Black already has a big problem.
Remember that different-colored bishops tend to be an advantage for the attacker, who exactly enacts the strategy I just described. (As the dude with the pair I of course would try the exactly opposite strategy - trying to get a position where both of your bishop just stare at pawns posteriors.)


How can I to hold on to the pawn plus for black in the Queen's Gambit Accepted?

Black can sometimes hold on to the Pawn if that is the goal.  Black has to play an early a6 and b5.  One possible variation is:

[FEN ""]
1. d4 d5 2. c4 dxc4 3. Nf3 a6 4. e3 b5

Although Black will hold on to the extra C-Pawn, White can counterattack with a4, b3, and Nc3.  Black has neglected development, and according to MegaBase 2012, White scores 60.6% from the diagrammed position with the move 5. a4.


How to convert PGN moves to long algebraic notation (in python)?

Would this be what you are looking for? PGN-extract (A command line utility)
http://www.cs.kent.ac.uk/people/staff/djb/pgn-extract/

I can see a flag in the feature doc that might help:

-W[cm|epd|halg|lalg|elalg|san|uci] - specify the output format to use
-Whalg is hyphenated long algebraic.
-Wlalg is long algebraic
-Welalg[PNBRQK] is enhanced long algebraic. Use the characters PNBRQK for language


Online:

Lichess and Internet Chess Club provide an online functionality to play blindfold chess and you can try to make a suggestion on their forums to organize a blindfold tournament.
This will probably be unofficial though and I do not now if that fills your expectations.

Local:

As @JossieCalderon said in his comment, you don't lose anything to make a suggestion in your local chess club about organizing a blindfold tournament.
You can even start by making an attempt through social media and see if enough people who want to participate appear.

Good luck :)

PS: Lichess blindfold team


How often does castling occur in grandmaster games?

If you are prepared to use standard Linux command-line tools like wc and grep then I think my free PGN processor, pgn-extract, will do much of the pre-processing necessary to count games in each category. Below is a basic bash script I put together as a proof of concept. It assumes your file of games is called inputfile.pgn - adjust as necessary, or pass it in as a command-line argument:

#!/bin/bash
# Output stats on castling.
src=inputfile.pgn
# Pre-process the games to allow textual analysis.
pgn-extract -C -V -N --notags --nochecks --linelength 10000 -s -o stripped.pgn ${src}
# Castling by white: detect a preceding move number.
grep '\. O-O ' stripped.pgn > Wkingside.pgn
grep '\. O-O-O ' stripped.pgn > Wqueenside.pgn
# Castling by black: detect no preceding move number.
grep '[^.] O-O ' stripped.pgn > Bkingside.pgn
grep '[^.] O-O-O ' stripped.pgn > Bqueenside.pgn
# Find games in which no castling occurred.
grep -v ' O-O ' stripped.pgn | grep -v ' O-O-O ' | grep -v '^$' > nocastle.pgn

# Output the FEN of the final position to include castling rights and
# look for the presence of rights.
pgn-extract -C -V -N --notags --nomovenumbers --linelength 10000 -s nocastle.pgn --dropply -1 -F | grep ' [wb] [KkQq]' > rights.txt

# Output the results - assumes valid Result tags in the source.
echo 'Number of games: ' `grep '^\[Result ' ${src} | wc -l`
echo 'W Kingside: ' `cat Wkingside.pgn | wc -l`
echo 'W Queenside: ' `cat Wqueenside.pgn | wc -l`
echo 'B Kingside: ' `cat Bkingside.pgn | wc -l`
echo 'B Queenside: ' `cat Bqueenside.pgn | wc -l`
echo 'Neither: ' `cat nocastle.pgn | wc -l`
echo 'Rights retained: ' `cat rights.txt | wc -l`

I tried the script on the KingBase database (Apr 2019) and, after removing broken games and duplicates got the following stats:

Number of games:  2072354
W Kingside:  1633762
W Queenside:  246158
B Kingside:  1670870
B Queenside:  128124
Neither:  69776
Rights retained:  24280

The 'neither' figure is about 3.4% while the 'rights retained' figure is about 1.2%. If games with 20 or fewer ply are removed then the 'neither' figure reduces to about 2.9% and the 'rights retained' figure to about 0.7%.


Learning chess over the board vs using software

You always pay attention when moving heavy wooden pieces. Work with PC can be faster but make sure you don't do it too superficially. Sometimes I just wheel the mouse, listen to the music and after checking twenty games of my opponent I don't know what is his first move. I like the old style learning, it isn't that powerful technically but still it can produce better results. The faster you play the lines, the less understanding you will get. That's why real pieces and books are not dead for training. I would go for watching videos on pc but I think I wouldn't read ebook on it.


Are there attempts at creating practical endgame tablebases?

There is a contradiction in terms in "only" generating practical endgame tablebases. We have to understand how tablebases are generated to see why.

Tablebases are generated by working backwards from the final mating/drawing positions, "retracting" moves rather than playing them forward. First, every possible final position is exhaustively listed. Then from each, we "retract" (take back) moves that could have been played. In doing so, we know a possible outcome of the resulting position (by playing forward to the final position again). Do this for all positions, and we know the ideal outcome of all of them.

Now what is a retraction? Pieces move backwards, so everything moves as in normal chess except pawns. Pieces can uncapture other pieces, leaving an extra piece on the board. Notably, pieces can unpromote into pawns.

Herein lies the problem. If you want to evaluate the "practical" endgames, you need to know all the final positions that could lead to them by retractions. If we agree KPPP v KB is a practical endgame (seems so), then we need to know the outcome of all KQQQ v KB endgames, since it might be the case that the only winning line is to reach a winning KQQQ v KB endgame. It is necessary to do these "trivial" endgames in order to do the practical ones.

(Preemptive counter-counterargument: not all KQQQ v KB positions are winning. Think of stalemates. This is another reason why we cannot handwave and say "all positions with this material balance are winning".)

Furthermore, the absurd KQQQ v KB might be necessary to correctly generate results for KQPP v KQBP or some dramatic pawn race endgame. If you don't check all the possible final positions (even absurd ones), you can never be sure that you didn't miss the only winning/drawing line.

The only possible "optimisation" of this sort you can do is to not generate, say K+6 v K endgames (which I think was the case for the 7-men tables, they skipped K+5 v K until everything else was done.)


Which notable players in chess history successfully used dubious openings?

If you really mean "dubious", then no one really fits this description since Steinitz, who liked to, for example, go for walks with his King when playing the King's Gambit as White. But people didn't really know better back then.

If you're willing to relax "dubious" to "offbeat", the first player that comes to mind is Bent Larsen, one of the strongest players in the world in the 1960s and 1970s. He regularly played 1.f4 and 1.b3 (often known now as Larsen's Opening), and also helped revive the Bishop's Opening and the Philidor Defense. None of these were regarded particularly seriously by top-level players at the time that he adopted them.

Before that, players like Réti and Nimzowitsch developed hypermodern theory, in which players tried to control the center from afar instead of occupying it with their pawns. Some players regarded this strategy as dubious but it shortly became clear that it was perfectly legitimate.


Looking for a Gata Kamsky quote - 'you must be playing a different kind of chess'

I remember this - it was an impressive moment. I don't remember who the players were, but the game was probably from the Open section. Vague recollections of proposed kingside maneuvers for Black, involving ...Qg8-h7 or something likewise extravagant. I don't remember the result of the game or if Kamsky's ideas were played. And unfortunately, most of the videos on the CCSCSL livestream channel from before 2014 seem to be gone.


What is the best way to sell old chess books?

If you live in the UK I would suggest the English Chess Forum. They have a "For Sale" thread. That way you are advertising to a dedicated audience. If you live in another country I would suggest you look for an equivalent forum in your country.

I would add that opening books devalue very quickly. A 10 year old opening book probably has value as a doorstop or paperweight only, unless it is a rare ancient first edition.


FIDE rating: how games are rated if a new list is published while playing a tournament

Option A is correct, option C applies to some tournaments, see below.
It is not explicitly stated in the FIDE Rating Regulations but the practice has always been that for rating purposes the rating valid at the starting date of the tournament is used. The only exception are tournaments that last longer then 90 days which have to be reported for rating every month

4.1 For tournaments, a period not greater than 90 days, except:
4.11 Leagues may be rated which last for a period greater than 90 days.
4.12 The QC may approve the rating of tournaments lasting more than 90 days.
4.13 For tournaments lasting more than 90 days, interim results must be reported on a monthly basis.

This is made more explicit in the International Title Regulations

1.46 Rating of Opponents
1.46a The Rating List in effect at the start of the tournament shall be used, see exception 1.15. ...

1.15 In tournaments which last longer than 90 days, the opponents’ ratings and titles used shall be those applying when the games were played.

Similar wording as in 1.46a would probably be helpful in the FIDE Rating Regulations.
Here are two examples:

Sallskapets Jubileums-KM 2016 lasted for exactly 90 days by a rough calculation and you can see that each player's rating is the same in all rounds (click on any player and you can see all their opponents have them with the same rating, the January rating in fact).
1. Bundesliga rounds 10-11 and 1. Bundesliga rounds 14-15 lasts for six months, it is reported every month and each month the current ratings are used.


Why does FIDE classical chess have a time limit for the first 40 moves?

Factually you ask two different things, "how" and "why", and maybe considering the "how" first makes things clearer.
Obviously, the FIDE time control is recent. In early history of chess there was no time control at all, the problem with that should be obvious. I am old enough to have played 40 moves/2 hours + adjournment, thus it's more recent than you might think.
Now to the "why". There is nothing special with 40 moves or two hours. Clearly 41 moves would be silly, man automatically thinks in round numbers. I daresay (experienced from thousands of tournament games, and only judging from the time spent by my opponents - I'm a notorical "blitzer") that 30 moves are too short: the hectic of time trouble would hit the midst of a game. 50 moves are too long - we are in the endgame already and could as well play it out. The same holds for "2 hours" which is not as carved in stone as you might think, I played lot of games in lower leagues with shorter, and also in higher with two time controls (40/2h+20/1h+rest/30m).
That said, the standard time control before the invention of electronic chess clocks was just a rounded compromise - almost anyone could live with it. Nowadays, indeed almost all games (at least the "top" ones) are played with Fischer bonus, which admittedly has advantages, especially for the referees (I'm one too and can acknowledge that).
tl;dr: No logic, just evolution, which includes clinging to accustomed numbers. If chess would be invented today, one might converge to another time control.


6.Nbd7 is played and often the lines transpose.
If Black continues to try and avoid e7-e6, his position, though solid, is less aggressive than the other lines.

Fischer said something like:

  "The Sicilian is not a defense, but rather a vicious counter-attack!"

so with 6...e6 7.f4 Black has options like 7...Qb6 entering the Poison Pawn Variation, or 7...b5 entering the Polugaevsky Variation which are considered some of the sharpest variations in chess theory.  Why spare White the worry of having to deal with either of these lines?

6...Nbd7 is playable and probably leads to equality as well but Black is delaying his counterplay if he avoids ...e6 for long.   Some issues are that Black would like to play Qc7 and then has to worry about Nd5 when if Nf6xd5 exd5 results in a favorable structure for White.


What does "White is down a rook for a pawn" mean?

It means that white is down a rook, and up a pawn compared to black. So black has one more rook than white, and white has one more pawn than black


What's the best answer to 1.d4 Nf6 2.c4 e6 3.a3?

This really comes down to what you're comfortable with. Both the Benoni and the QGD are good options, precisely because of the reason you mention: a3 isn't really useful for White in those openings, so you'll be playing lines with a tempo up. According to chessgames.com, Black is already better. Which line (3... d5 or 3... c5) is better is just a matter of personal preference.

3... b6 is of course playable, and Black scores 50%, but it allows White to transpose to one of the main lines of the Queen's Indian with 4. Nf3.


Is it bad etiquette to keep playing in a clearly hopeless position?

As a general rule, if something is not done out of malice then it's not bad etiquette in my book (especially if it's allowed in the rules). So if all you do is play on in a lost position, then I don't see how anyone could complain; for instance, should a novice not be allowed to play on until checkmate? That would be absurd, no matter who said novice were facing!

The only unsportsmanlike behaviour I've witnessed in this regard was a player in an OTB tournament just sitting and waiting for his clock to run out when the position became hopeless, since his intent was obviously to spite his opponent and waste their time. If he had been making moves I wouldn't even have reacted, but since he was just doing it to annoy his opponent it was a clear act of malice and therefore bad etiquette.


How do age and initial rating correlate to decline in playing strength with age?

I looked at the data briefly and got some interesting conclusions.

I used data from FIDE webpage for january in years 2006-2019.

I calculated each player's rating change in consecutive years and used player's age in the first of the two as the age when this rating change occurred. Then I simply calculated the average. The result is this:

As you can see, players are on average gaining rating only until the age of 27, and afterwards they tend to slowly lose rating. Children gain the most rating per year, which is very intuitive.

Rating range 19-90 from up close:

Rating loss increase looks linear.

Cumulative rating change:

This is of course cumulative change since the age of 10.

Secondly, I did the same thing but separated players into groups. I looked at each of their entry in the data and put them into respective categories according to the maximum rating achieved in it: which might not be their actual peak rating, but should be a good indication of their top strength.

Gains are much larger here. Might be due to the fact that the negative contribution of sub-1500 players isn't included. Intuitively, higher rated players have higher average rating gains, but the decline rate seems to be similar regardless of the strength.

The linear range up close.

Cumulative again.


When (if ever) was it a rule that pawn promotion was optional?

Dummy Pawns
Today, it is little known that for forty years at the height of the British Empire, dummy pawns were the scourge of tournament play, and even grandmasters ran scared. (Possible exaggeration here.)
The heresy raged from 1862-1904. See Eminent Victorian Chess Players: Ten Biographies by Tim Harding. However, the origins of the dummy pawn goes back to at least 1832 and before.
Timeline of known events
(+/- indicate events pro/con the dummy pawn concept)
1832 + the earliest known reference to the dummy pawn is printed in “A new treatise of chess” by George Walker
1847 + the first known chess problem with the dummy pawn in it occurs in the American Chess Magazine
1851 + arrival in London, first appearing in the “The Chess Player’s Chronicle,” and called “The Revolutionary”
1854 - an example by Alexander Petroff appears in “Règles du jeu des échecs” in which the concept was denounced
1860 - Howard Staunton in his "Chess Praxis" wrote "no one will consider [dummy pawns] worthy of serious consideration."
1862 + International London Congress - provides an official rule for dummy pawns
1865 - William Pavitt, UK, explores the effects on chess composition in “The Chess World”. He describes it as "an exquisite stroke of chess legislation," but still condemns the concept.
1870 + Baden Congress - takes same line as London Congress of 1862.
1876 - new edition of Staunton's "Chess Praxis" - his rules still say no dummy pawns
1879 - American Chess Journal - "a frivolous and undesirable innovation"
1880 + Fred Thompson, in “Pawn on 8 In Chess Problems,” advocates for them as aids in chess composition
1883 - London International Chess Congress bans dummy pawns
1883 + Francis C. Collins composes a s#2 allumwandlung for “The New Zealand Mail”
1889 + Steinitz - supports London 1862 decision, and reports that so have many Congresses
1894 + "The Chess Pocket Manual" describes the "famous Dummy Pawn rule"
1898 + a spectacular Sam Loyd #3 composition
1900 + a superb #4 by E. J. de Savornin Lohman
1895 - the legendary Hastings congress bans dummy Pawns
1903 - there is an unsupported statement that the reign of dummy Pawns ended in this year ([http://www.chess-poster.com/english/history/the_pawn.htm][1])
1904 - founding of British Chess Federation, which according to Harding published the rules that finally exiled the monstrous dummy pawns to history
1913 + leading problemist Thomas R. Dawson composes a classic study with 3 dummy pawn promotions by White
1996 + John Beasley publishes a dummy pawn promotion study in EBUR
2017 + dummy pawns gains new life in chess.com and Matplus.net forums
2018 + chess.stackexchange.com diagram editor (still) supports dummy pawns
2020 + Popeye & Jacobi problem engines (still) support dummy pawns

See dummy pawns in action in our own heretical diagram editor below! (Except for the Ponziani game which is even more bonkers, and cannot therefore be animated correctly.)
1832: A Concept Develops
The origin of dummy pawns is mysterious and unknown. It most likely occurred in the early 19th century though. However, there is some sparse record of it. The earliest known reference to the dummy pawn is in 1832 from the book “A new treatise of chess” by George Walker.
On top of page 15, under the section “No. XX.,” pawn promotion is briefly described.
“When you have advanced the pawn to the extreme rank, or eighth square of the board, it immediately assumes the power of any piece you chuse [sic]. (The constitution of the game, would, of course, not allow of your demanding a second King, but you may have as many Queens, Knights, &c. as you can get. En passant, I may be allowed to add, that it is presumed from the wording of the law, you might not call for a pawn, and replace it at its own square; but might certainly, for argument's sake, leave it as its eight square, as a Pawn, without exchanging it for an piece.)”
The text we have put in bold does not say “dummy pawn” exactly, but the language is clear enough. Dummy pawn is the central subject.
1847: A Misty Appearance In America
The first known chess problem that uses the dummy pawn is from “The American Chess Magazine” in the year 1847. On page 113 the following problem was shown with the attached question.
[Title "F. Leake - American Chess Magazine 1847, Can White force checkmate in five moves? "]
[FEN "2B5/8/1K1k4/4pP1N/3pP3/Pp1P4/p7/7R w - - 0 1"]

It says: “ A question of great importance - one which is not provided for in the laws of the game of Chess, and to decide which we know of no precedent- is here involved. Can White force Checkmate in five moves? That's the question."
If Black is obligated to promote to a piece, then there is a mate in 5: 1. f6! b2 2. Rb1 a1=B 3. Rxb2 Bxb2 4. Ng4/g7 ~ 5. Nf5/e8#. However, if Black may keep it as a pawn, then there is no mate in 5. There is a unique mate in 6 though: 1. f6! b2 2. Rb1 a1=Pawn 3. Kb7 Kc5 4. f7 Kb5 5. f8=Q Ka5,Ka4 6. Qb4#
On pages 136-139 appears correspondence giving opinions as to whether or not there is a mate in 5.
No: “(Skipped text) I presume that the question you raise is this: When a Pawn reaches the eighth square, is the player obliged to change it at once for a Piece, or has he the option of allowing it to remain dead on the eighth square? In my opinion, he is obliged to change it at once for a Piece ; he has no option but in the choice of the Piece so exchanged. The Twenty-third Law of Chess, according to Walker's Treatise, (1842,) is :— Directly the Pawn attains the eighth square, or extreme rank of the board, it must be replaced by a Queen, Rook, Knight, or Bishop, at the option of its owner; and this without regard to whatsoever Pieces he may already have on the board. Should you not replace the Pawn with a Piece, before your opponent move, he may take it off the board as forfeited. (Skipped text). Though you appear to think this a very nice question, I have but little doubt as to the nature of your decision, should you think proper to make one. And with all due deference to your well-earned reputation as a Chess-lawyer, I will venture to risk the opinion, that the " big wigs" in London will be surprised that you should regard the question as one unprovided for in the laws of Chess." - Philo-Chess
Yes: “(Skipped text) For myself, however, I incline to a different opinion. The Checkmate in this case cannot be forced in five moves, unless the Pawn, on reaching the "royal line," loses its character as a Pawn, and immediately and necessarily becomes a Piece of some kind; or unless Black is compelled, by some law of the game, to replace the Pawn at once by some Piece. (Skipped text) It is obvious that the right of promotion is granted as a favor or privilege, and that upon the assumption that a Piece is of greater value than a Pawn. Why, then, limit this privilege, by confining the choice to a Piece? Why, especially, require the player, who is entitled to a reward for his skill and success in conducting his Pawn to the "royal line," to submit to a positive disadvantage, by compelling him to exchange it for a Piece of inferior value to him? Finally and conclusively, the rule, strictly construed, is anti-republican-and this is a "free country!" Why should the Pawn have "greatness thrust upon him If he is satisfied with untitled merit, why not permit him to indulge his tastes for private station? Why elevate him, against his inclination, to a rank to which he does not aspire?“ - A.D.P.
The wonder is that this problem is much more sophisticated than any other dummy pawn problem that would be made for nearly two decades, until Pavitt came along with his 5-mover in 1865.
1851: A Boost In London
The dummy pawn, 4 years later, once more made an appearance on the other side of the Atlantic Ocean in Edward Winter managed to find the first mention of a dummy pawn endgame study in England in C.N. 7619. In the September 20, 1851 edition of “The Chess Players Chronicles,” the following problem called “The Revolutionary” appeared. This is where the dummy pawn truly started its reign.
[Title "Josef Kling & Bernhard Horwitz - The Chess Player 1851, Revolutionary Question XIX: How can White draw?"]
[FEN "r7/1Pp5/2P3p1/8/6pb/4p1kB/4P1p1/6K1 w - - 0 1"]

The solution, which was given in a week later, stated: “The solution of No. 19 is Pawn takes Rook, remaining a pawn. It may seem ridiculous to many chess-players, but we think candidly that, when first the rules were laid down, nobody thought of such a case, or else the rules would be a little more precise on that point."
In the correspondence section of the 9/20 issue the editors also said “ We are of opinion that a pawn, when reaching his eighth’s square, is entitled to become any piece the player thinks best; and, naturally enough, if it prove disadvantageous to become a piece, it may still remain a pawn. (See Diagram 19.) This question among others, we thought, should have been discussed at the Tournament.”
1854: Spread In Europe & Rejection
From 1851 onward, the idea of the dummy pawn seems to spread across Europe. One indication is the appearance of another dummy pawn problem, this one also being White to play and draw, that was created by the Russian composer Alexander Petroff and published in the 1854 French book Règles du jeu des échecs. On page 97, the problem was given.
[Title "Alexander Petroff - Règles du jeu des échecs 1854, White to play and draw"]
[FEN "rn6/pp2n3/2p5/P4k2/8/6p1/6Pp/7K w - - 0 1"]

1. a6 Nd5 2. axb7 Nf6 3. bxa8 null

However, this problem is flawed because Black can play 2... Nf4!, 3. bxa8 Nxg2 4. Kxg2 Kg4, and Black wins. White doesn't win even if they promote-3. bxa8=Q Nd3 4. Qxa7 Nf2+ 5. Qxf2 gxf2 6. g4+ Kxg4 winning.
The French text, roughly translates, reads: “This subject, we must say that Mr. Petroff communicated to us the following problem, in which, supposing the best possible blows on the part of the blacks, the whites could not postpone the game, unless they were allowed to refuse any promotion to their pawn entered lady, that is to say to leave it pawn. (Diagram of the problem.) On this occasion, Mr. Petroff asks us to submit to the judgment of the European authorities in matters of gambling, if it would not be advisable to introduce into the regulations a clause which would allow the possessor of a pawn entered to queen, to renounce to any increase in its forces, leaving this pawn inactive and immobile, as a pawn, until it is taken or until the end of the game?
(Skipped Text)
“For its part, the Society of Saint Petersburg Chess Lovers did not believe that it could accept this opinion (expressed in the form of doubt by Mr. Petroff himself), contrary to the fundamental principle of the game, which 'does not admit the existence of pawns to the strips of the chessboard originally occupied by the pieces.'"
This shows that the dummy spread like wild fire, relatively speaking for the times, and within 3 years it was already an outrage in at least France and Russia. It would take awhile for the English to get their turn.
1860: Staunton, bastion of orthodoxy
The "dummy pawn rule" was not part of the official rules up to 1860. See "Chess Praxis" by Howard Staunton 1860. Staunton was a very influential player and author, and in this book codified the Laws of Chess, in a way which is still recognizable in the style of the FIDE Laws today. On page xi, in the Introduction he lists chronologically the many antecedents of his work from Ruy Lopez in 1561, to the 1850s.
*Page 6, Queening a Pawn: “When a Pawn has reached the eighth or last square on its file, it immediately assumes the name and power of any Piece its player may select, except a King, whether such Piece have previously been lost or not; and, if the player does not select a Piece, such Pawn is always to be considered a Queen.”
On page xii, he had defined "Piece" to explicitly exclude pawn. The real fun comes later:
Chapter 4, "A Queened Pawn: “On this subject great difference of opinion prevails, but the rule laid down in the text is that universally observed in practice. In the middle ages, as we have previously explained, the Queen could only move one square at a time diagonally. She was, therefore, by far the weakest piece on the Board. And the ancient law, which required that every Pawn pushed on to the eighth square should become a Queen, was really a restrictive enactment, since it gave the promoted Pawn as little additional power as the conversion could offer. But the spirit of the modern game is to regard the Queening of a Pawn as the highest feat a player can accomplish, and to reward it with the greatest possible advantage. So that a player in the present day is not only allowed to select a second or third Queen with its enormously extended power, but may choose any other Piece that would be more advantageous in a particular position. Various modifications of this law have existed in different places and at different times. It has been held, for example, that the Pawn should only acquire the power of the Piece on to whose square it had been played, or of a Piece already lost. It  has also been proposed to limit the conversion to either a Knight or a Queen, as the latter comprises the power of Rook and Bishop; and the Pawn has sometimes been required to perform certain additional moves before becoming entitled to the privileges of a Piece. The most plausible of the regulations is that the Pawn should only supply the place of a Piece already lost, so as to avoid, what Philidor so violently denounced, plurality of pieces. But then comes the difficulty of providing for the case where a Pawn has reached the eighth square before any Piece has been lost. It has been proposed to leave such a Pawn, as it were, dormant, until a capture should have made among the Pieces a vacancy for it to supply. Ponziani, an advocate of this regulation, has given the following little game as an example of it.”
Example of non-standard castling & promotion
 [Title "Ponziani scheme - White to move"]
 [FEN "Bn1qk1nr/p1p2ppp/8/8/4P2b/5N1b/PPPP3P/RNBQ1rK1 w k - 0 1"]

1. e4 e5 2. f4 exf4 3. Nf3 Be7 4. Bc4 Bh4+ 5. g3 fxg3 6. Kh1&Rf1 d5 Italian style castling!
7. Bxd5 Bh3 8. Bxb7 g2+ 9. Kg1 gxf1 without promoting
10. Bxa8 Bf2# & f1=R# only now does pawn f1 promote to a rook
“In this game the black Pawn, which attained the eighth square on its ninth move, neither gave mate nor check, because the player had lost no Piece into which it could be converted, and it was not in a situation to check as a Pawn. But as White chose to capture the Rook on his tenth move, Black plays down the Bishop with one check, giving another and mate, with the Pawn now become a Rook in place of that captured. There is so much of the absurd about such a finale as this that no one will consider it worthy of serious examination, and it is only mentioned as a matter of curiosity.”
1862: The Madness Becomes Official
As described in the Edward Winter link in another answer, the dummy pawn rule was codified in the International Congress of London in 1862, despite Staunton's outrage. For a generation, the war raged between the two camps, echoing the chaos in the European political space at this time. English chess papers would bicker about it for decades to come, with numerous joke problems and articles,  with most condemning the dummy pawn.
1865: Some Chess Composers Grumble
In 1865, 3 years after the passing of the law allowing the dummy pawn, an early article by William Pavitt against the dummy pawn appeared in the “The Chess World”.
Pavitt gave this simple mate in three he created that worked under normal promotion rules
[Title "William Pavitt - The Chess World 1865, Mate in 3"]
[FEN "K7/2N5/2p5/k1P3R1/p4N2/P2P4/6p1/8 w - - 0 1"]

1. Ng6! g1=Q 2. Ne5 Qc1 3. Nxc6#

However, in essence, with the dummy promotion rule, the problem wouldn’t work as there is no mate in two. He showed a mate in 5 to show how the problem would have to be corrected to conform with the dummy pawn. (Note that this is a correction the original created by James Malcom as the original is incorrect).
[Title "William Pavitt (corrected J. Malcom 2020), Mate in 5"]
[FEN "8/K1N5/2p5/k1P5/p7/P2PP3/3p2pN/3B4 w - - 0 1"]

1. Ng4 g1 2. Bf3 d1 3. Bd5 cxd5 4. Ne5 d4 5. Nc4#

Pavitt showed these problems to give examples on how allowing the dummy pawn would greatly affect chess problems, and he condemned the concept as negative.
Most chess composers in the chess problem world were eventually set against the dummy pawn due to how it would interfere with known chess problem and the needless work that would be needed to incorporate it in. An occasional exception, i.e. Christmas and trick problems that intentionally used it, was generally accepted for the humor. In fact, many problem tournaments specified to rules to disallow the dummy pawn.
1870: Baden
A typical data point from this dark time is the Baden Chess Congress of 1870, which adopted the 1862 rules (source). An article covering this begins attractively:
“Unmoved by the shrill notes of the war trumpets sounding in their ears, the Chess players have commenced their mimic strife in Baden.“
1876: Staunton
In the mean time, Staunton came out with another edition of his Praxis (source). He did not mention the 1862 rules, but he did give the previously discussed 1854 example by Petroff.
1880: A Rare Friend To The Dummy
However, not everyone gave disdain to the dummy problem. A few chess composers thought that it should be allowed. An old article by Fredrick Thompson, published in 1880 in “Chess Player's Annual And Club Directory,” called on “Pawn On 8 In Chess Problems” gives an insight into the supporters of the dummy pawn. In his article. Thompson advocated for the dummy pawn to be allowed in chess problems.
Various reasons are given, the most interesting perhaps being this: “ The main objection to P on 8 is, that it breaks a fundamental law of Chess. So it would if pawn stood on square 1, but on square 8, in the enemy's territory, is quite another thing. As Staunton in his Praxis says—" The ancient idea supposed the Chess Board divided into two belligerent kingdoms." Have common soldiers never mounted guard in the palace of a foreign potentate at the conqueror's behest? Ought pawn to be played to 8 at all if he may not remain there? His captain bids him stand sentinel as a private soldier, and it is not for the discomfited foe to say him nay. Ought pawn to attack a piece or check the King from square 7, if he has no business on 8?”
The logic is that if the pawn has power on the 7th rank as a pawn, why should can it not extend its rights as a pawn on the 8th rank?
A more straightforward reason is also given: “The present pawn-queening law bristles with innovations upon ancient usage. As Mr. Staunton wrote on March 18, 1865—"The old laws from which you quote, have been constantly modified of late years." Fundamental law, forsooth! The law never had a bottom. No one will deny the use of pawn on 8 in problems if pawn on 8 is permissible in play. The " Competent authority " for the laws of Chess must be players, not problem composers, for the laws, of the game govern the problemist, not the problemist the laws of the game.”
Lastly, he advocates for it as to prevent cooks in chess problem, to make possible otherwise impossible ideas realizable at last. He gives a problem to illustrate his defense of the dummy pawn, since it would be cooked without the pawn on c8, since without there would be a cook starting with 1. Qc8+.
[Title "Fredrick Thompson, Mate in 3"]
[FEN "2PQ4/6p1/3P2B1/3Pk3/8/2N1N1P1/8/7K w - - 0 1"]

He ends with this: “ I claim, therefore, P on 8 in Chess strategy, and conclude this paper with a problem commenced in July, 1879. (Skipped text). Dropping the men one square down the board also produces a cook, in fact the dead pawn saves the problem from being relegated to the waste basket. I consider this one of the best compositions I have put together during a practice of thirty years, and I fail to see why it should be treated to Lynch-law, when the queening-a-pawn rule is to "reward it with the greatest possible advantage."
1883: London Congress
Another data point is the London International Congress of 1883, where the rules include:
“10. A Pawn reaching the eighth square must be named as a Queen or Piece, at the option of player, independent of the number of Pieces on the board. The created Queen or Piece acts immediately in its new capacity. Until the Pawn has been so named, the move is incomplete.”
This is the first occurrence I've ever seen a usage of Piece to exclude the Queen! However, it's clear that dummy pawns are on the wane.
1883: Far Reaches-The Dummy Pawn’s Travels
One example that can be found of how far the dummy pawn reached is a problem from the 3/10/1883 edition of the “New Zealand Mail.” New Zealand was then part of the British Empire, is so not so surprising that the dummy pawn got that far, but it is pretty far though!
[Title "Francis C. Collins - New Zealand Mail 3/10/1883, Selfmate in 2"]
[FEN "1n3R1n/3p1p2/B1pP1Pp1/2B1K1P1/2r5/3k4/NR2p1Q1/8 w - - 0 1"]

The point is that capturing the b8 knight fails because Black can then promote to a pawn and there is no selfmate after that.  The solution is 1. Rxf7!, such that after e1=P, the move. 2. Rxb8 forces 2... Nxf7#.
The solution, printed in the 4/21/1883 edition, says this: "This position has been composed by Mr. Collins in accordance with the British Chess Association’s 13th Law: —“When a pawn has reached the eighth square, the player has the option of selecting a piece, whether such piece has been previously lost or not, whose name and powers it shall then assume, or of deciding that it shall remain a Pawn.” This rule of the “dummy pawn” has never met with much favour amongst chess-players, and there are very few clubs or societies which observe it. We have received no correct solution to the problem (which is a most ingenious one), the result doubtless of the non-acquaintance by our friends of such a rule as the foregoing in any of the codes of chess laws."
This shows just how weak of an entity the dummy pawn has become and how very few looked upon it with favor.
1895: Hastings Congress
By the time of the famous Hastings Congress in 1895, dummy pawns are clearly gone from serious play. The Congress rules adopt exactly the same wording as London 1883. (All attendees were searched to make sure no dummy pawns were being smuggled into the venue.)
1898: Sam Loyd #3
In what is widely known as the last hurrah, no discussion of the dummy pawn period would be complete without the following beautiful problem by the American composer Sam Loyd.
[Title "Sam Loyd - American Chess Magazine, Mate in 3"]
[FEN "N1Br4/2Pb1P2/3k4/1P2R3/1P2K3/B7/8/8 w - - 0 1"]

1. cxd8!
(1. cxd8=Q/R? stalemate)
(1. cxd8=B? Bf5+)
(1. cxd8=N? Bc6+)
threatening 2. f8=Q/B#
(1... Bf5+ 2. Rxf5 Ke7 3. f8=Q#)
(1... Bc6+ 2. bxc6 Kxc6 3. b5#)
(1... Bxc8 2. f8=Q+ Kd7 3. Qe7#)
(1... Bxb5? 2. Re6#)

1900: An Ingenious #4
But in fact Loyd's was only the penultimate hurrah. Two years later the brilliant but little-known E. J. Lohman produced this gem, which is as ingenious as Loyd’s #3. This is what should be known as the last hurrah of the dummy pawn, the pinnacle of the times when you could make a position and legally solve it by promotion to a dummy pawn.
[Title "E. J. de Savornin Lohman - De Amsterdammer 02/09/1900, Mate in 4"]
[FEN "2B5/1pR1P3/1P1k4/8/2K5/5P2/8/8 w - - 0 1"]

1. e8! Ke5 2. Rf7 Kd6 3. f4 Kc6 4. Rf6#
(1. e8=Q/R? stalemate!)
(1. e8=N+? Ke5 2. Rf7 stalemate!)
(1. e8=B? Ke5 2. Rf7 Kd6 3. f4 stalemate!)

1904: The Mischief Ends
But it was only with the arrival of the British Chess Federation that the final nail in the coffin was driven home. There is still some lack of clarity as to the precise year this happened, but it was around 1904.
1913: ...And Yet
Nearly a decade after the dummy pawn was finally killed off in law, the famous fairy chess composer Thomas R. Dawson took some time to make a drawing study with it. White must create three dummy pawns in order the achieve the draw via self-stalemate!
[Title "Thomas R. Dawson - The Chess Amateur 1913, White to move and draw"]
[FEN "6K1/6PP/3p2PP/3P1ppp/8/ppp5/qrp5/1rk5 w - - 0 1"]

1. Kh8 Kd2 2. g8 Re1 3. g7 Re6 4. dxe6 Rb1 5. e7 b2 6. e8 Qxg8+ 7. hxg8 null 8. h7 null

Afterward, the dummy pawn slowly faded into history, only mentioned now and then, until the dawn of the Internet.
1996: A Lone Bright Spot
In 1996, the dummy pawn had another brief period of relevance when John Beasley made a small study in which the only way for White to win is to promote to a pawn. It is the first known dummy problem in which White wins since the Loyd #3-nearly a century! I will leave to you figure out the reasons to avoid promoting.
[Title "John Beasley - EBUR 1996, White to move and win"]
[FEN "5r1K/2k1P3/3N1Bqp/N2Q1B1P/8/8/8/1R6 w - - 0 1"]

2017: Just For Fun
The Internet has allowed many to create and share their own dummy pawn problems. While there is no doubt many problems been created, perhaps the pinnacle of achievement was when Peter Wong created an entirely new problem in which White wins by promotion to a pawn!
The problem was shared on the Matplus.net forums in November, 2017, although. the composer has originally shared somewhere on chess.com.
The chess composer Geir Sune Tallaksen Østmoe managed to add a golden touch to Peter Wong in that it is in both sides best interest to promote to a pawn!
[Title "Geir Sune Tallaksen Østmoe & Peter Wong - Matplus 11/12/17, Black to move and White to win"]
[FEN "5qnk/3pPB2/1p1p1N2/1pbK1NP1/1p1pP3/1P1P4/6p1/7R b - - 0 1"]
[startflipped ""]

1. gxh1! exf8!

White easily wins with an extra piece. The full solution and the refutations of each promotion can be viewed here.
Also from the same forum, here are two possible 6-piece settings for dummy pawn draw:
[Title "ichai - MatPlus 7/2/2020, White to move and draw"]
[FEN "8/2P5/8/8/8/2r5/p1r5/K1k5 w - - 0 1"]

1. c8!
(1. c8=Q? Rb3)

And the current economy record-holder:
[Title "A.Buchanan - MatPlus 13/5/2020, White to move and draw"]
[FEN "7K/5rPp/7k/8/8/8/6p1/8 w - - 0 1"]

1. g8!
(1. g8=Q? g1=Q! 2. Qxg1 Rf8+ 3. Qg8 Rxg8+ 4. Kxg8 Kg6!
    (2. Qxf7 Qd4+ 3. Kg8 Qd8+ 4. Qf8+ Qxf8+)
    (2. Qf8+ Rxf8#)
    (2. Qg7+ Qxg7#)
    (2. Qxh7+ Rxh7#)
    (2. Qg5+ Kxg5)
    (2. Qg6+ Kxg6,hxg6))

Will the dummy pawn rise again?
It seems unlikely that FIDE will introduce the dummy pawn for over the board play, although it would be cool if they did. For compositions, dummy pawn promotion, as the ultimate under-promotion, is paradoxical and dramatic: exactly what a problem chess move should be. However, introducing a 5th promotion option would render incomplete the vast range of allumwandlung studies, including solutions to the famous Babson task. So this novelty seems unlikely to happen.
Where Can I Find Dummy Pawn Problems?
Currently, the largest known catalogue of dummy pawn problems is on the Die Schwalbe Chess Problem Database Server, known as the "Schwalbe PDB for short. Searching "K='dummy pawn' in the search function currently brings up a list of 63 dummy pawn problems, from across the 19th-21st centuries. It is but a small sample of what exists out there.
Extensive edits and additions were carried out by Rewan Demontay May 6, 2020.
Some follow-up mods by Laska subsequently: let's keep building it!
Addendum 8/31/2020-The history of the dummy pawn has been pushed back to 1832.


Are all grandmasters capable of playing blindfold?

As of this post all super grandmasters can play blindfold. For young GMs who are just starting out playing blindfold, they may not be super good at first but they should be able to pick it up quickly. Also, for old GM's it might be harder for them to play blindfold, as short term memory and spatial reasoning might be diminished. But most, if not all, GMs should be able to play blindfold chess.