Coefficients of Terms Equidistant from Beginning and End

Q. Which of the following is (are) polynomial function(s)?

1. $f\left(x\right)=x^3-2$
2. $f\left(x\right)=5$
3. $f\left(x\right)=a{x}^2+4x-4$, where $a\in R$
4. $f\left(x\right)=\frac{1}{x}-2$

Q. The Arithmetic Mean of the co-efficients in the expansion of $(1+x{)}^{30}$ is

1. $\frac{2^{30}}{31}$
2. $\frac{2^{30}+1}{31}$
3. $\frac{2^{31}}{31}$
4. $\frac{2^{30}}{30}$