If I have the following information
(A) 5%, 10%, 15%, 4% = 5+10+15+4 = 34%
Sum 34%/4 Years = Average Return 8.5%

How do I find the Variance,
Standard deviation
Coefficient variation

Wikipedia has a whole section on standard deviation. The variance is the square of the standard deviation.

Standard deviation - Wikipedia, the free encyclopedia

Simply subtract the average from each value and square it. Add all of the squares and divide by (usually) 1 less than the number of items. In this case, divide by 3. You've now calculated the variance. Take the square root of the value and you have the standard deviation.