Two hard indices questions, (what is power to a power of fraction) and (how is $(2^x)^2 = 4^x $)

Question

The answer for question 1) is $2^{3b+6}$

Question 2 I only don't get the $Y^2$ bit

Answer 1

Hint for the 1st: $\left( 4^{b+2}\right)^{\frac{3}{2}}=\left( 2^{2b+4}\right)^{\frac{3}{2}}=2^{3b+6}$.