Q: Limit On Number Of Simultaneous Actions? Sometimes when things are getting intense I will try to hit every button in short succession (including multiple mouse buttons). Oftimes I find that the activated item is not actually activated, and I can never tell if I'm messing up the click or if league is ignoring some of the actions. Is there a limit on the number of actions your champ can do at once (abilities and activated items)?
e.g. A Xin Zhao with all 4 abilities and an activated item, can you mash the 3 non-ult abilities and the activated item at the same time?
NOTE: I'm not talking about casting lots of abilities at once, I know that there are plenty that can't be cast at the same time. I'm also not talking about keyboard rollover as I have PS/2 keyboard.

A: Alright so, as far as anyone can tell, there is no global cooldown in league. Just like in the answer to the question Colin D posted, almost every ability in the game has a cast timer as well as a cooldown. Some abilities have a short cooldown timer to prevent them from being spammed instantly (akali's ult). There are few exceptions to this, most being instant self cast abilities. Fiora's deflect and attack speed boost are just one example of this. 
In regards to your issue of actives not being activated, I recommend smartcasting your item bar. I have my '2' key smartcasted for whenever I have BOTRK because its a lot easier to press 2 in the general area of an enemy instead of trying to focus on trying to click activate it on them in the heat of battle while trying to use abilities at the same time. 
To answer your main question, there is no (documented) limit to how many abilities you can do at once. Your only limitations are cast times and cooldowns. You can remove a lot of these errors by learning to smartcast if you haven't already done so.
