Can any one give a generalization of the following properties in a single proof? I have checked the results, which I have given below by trial and error method. I am looking for a general proof, which will cover the all my results below:


Every third Fibonacci number is even.
3 divides every 4th Fibonacci number.
5 divides every 5th Fibonacci number.
4 divides every 6th Fibonacci number.
13 divides every 7th Fibonacci number.
7 divides every 8th Fibonacci number.
17 divides every 9th Fibonacci number.
11 divides every 10th Fibonacci number.
6, 9, 12 and 16 divides every 12th Fibonacci number.
29 divides every 14th Fibonacci number.
10 and 61 divides every 15th Fibonacci number.
15 divides every 20th Fibonacci number.


Many of the divisibility properties of Fibonacci numbers follow from the fact that they comprise a divisibility sequence, i.e. $\rm\,m\,|\,n\ \Rightarrow\ F_m\,|\,F_n.\,$  All of your statements above are special cases of this, e.g. $\rm\,F_{15} = 610,\,$ so $\rm\,15\,|\,n\ \Rightarrow\ F_{15}\,|\,F_n\,\Rightarrow\,610\,|\,F_n,\,$ which is precisely your statement $11,\,$ that $10$ and $61$ divide every $15\,$'th Fibonacci number.
In fact $\rm\,F_n\,$ is strong divisibility sequence, i.e. $\rm\,(F_m,F_n) = F_{(m,n)},\,$ i.e. $\rm\,gcd(F_m,F_n) = F_{\gcd(m,n)}.\,$ This stronger property specializes to the above property if $\rm\,m\mid n\,\ (\!\!\iff \gcd(m,n) = m\,\!).\,$ The proof is not  difficult. Here is a straightforward way to proceed. Recall the Fibonacci addition law $\rm\,F_{n+m} =F_{n+1}\,F_m + F_n\,F_{m-1}.\,$ Applying the shift $\rm\,n\to n-m\ $ this addition law becomes $\rm\,\color{#c00}{F_n}  = F_{n-m+1}\,F_m  + F_{n-m}\,F_{m-1}\!\color{#c00}{\equiv F_{n-m}\,F_{m-1}}\pmod{\!F_m}.\,$ So for $\rm\,k=m-1\,$ we may invoke the Theorem below to conclude that $\rm\,f_n  = F_n\,$ is a strong divisibility sequence.
Theorem $ $  Let $\rm\ f_n\, $ be an integer sequence such that $\rm\ f_{\:\!0} =\, 0,\ f_1 = 1\ $ and such that for all $\rm\,n > m\,$ holds  $\rm\ \, \color{#c00}{f_n\equiv\, f_{\,k}\ f_{n-m}}\,\ (mod\ f_m)\ $ for some $\rm\,k < n,\ (k,m)\, =\, 1.\, $  Then $\rm\ (f_n,f_m) = f_{\,(n,\,m)} $
Proof $\ $ By induction on  $\rm\,n + m.\,$ The theorem is trivially true if $\rm\ n = m\ $ or $\rm\ n = 0\ $ or $\rm\, m = 0.\,$ Assume wlog $\rm\,n > m > 0.\,$  Since $\rm\,k\!+\!m < n\!+\!m,\,$ by induction $\rm\,(f_{\,k},f_m)=f_{\,(k,\,m)}\!=\,f_1 = 1.\,$  So $\rm\ (\color{#c00}{f_n},\,f_m)\overset{\color{#90f}R}=\ (\color{#c00}{f_{\,k}\,f_{n-m}},\,f_m)\, \!\overset{\color{#0a0}E}= (f_{n-m},\,f_m)\, =\, f_{\,(n-m,\,m)} =\, f_{\,(n,\,m)} $ follows by induction  (which applies here since $\rm\,(n-m)+m\,  <\, n+m\,\!),\,$ and by employing  well-known gcd laws, namely $\rm\,\color{#90f}R\!:\ (\color{#c00}a,b) = (\color{#c00}a',\,b)\ \ if\ \ \color{#c00}{a\equiv a'}\pmod{b}\ $ and $\rm\,\color{#0a0}E\!:\ (\color{c00}c\:\!a,b) = (a,b)\,$ if $\rm\,(c,b) = 1.\ \ $ QED
You may find it insightful to simultaneously examine other strong divisibility sequences, e.g. see my this post on $\rm\,f_n = (x^n-1)/(x-1).\,$ In this case $\rm\, \gcd(f_m,f_n) = f_{\,\gcd(m,n)}\,$ may be interpreted as a $\rm\,q$-analog of the integer Bezout identity, for example
$$\begin{align} \rm\displaystyle\ \color{#c00}3 = (\color{#0a0}{15},\color{#90f}{21})\,\  \leadsto\,\ f_{\:\!\large\color{#c00}3\,} &\rm =\, a\, f_{\:\!\large\color{#0a0}{15}}+b\, f_{\:\!\large\color{#90f}{21}},\,\ \text{explicitly:}\\[.3em] 
\rm \frac{x^{\large \color{#c00}3}-1}{x-1} \,&\rm =\, (x^{{15}} + x^9 + 1)\, \frac{x^{\large\color{#0a0}{15}}-1}{x-1} - (x^9+x^3)\, \frac{x^{\large\color{#90f}{21}}-1}{x-1} \end{align}\qquad$$
Generally see this answer for $\rm\, f_n = (x^n-y^n)/(x-y)$.
