What is the sum of the coefficients of $(x^2 - x - 1)^{99}$?

The value of $4 \{^nC_1 + 4 \cdot ^nC_2 + 4^2 \cdot ^nC_3 + \dots + 4^{n-1} \cdot ^nC_n\}$ is:

The coefficient of $x^n$ in the expansion of $(1 + x + x^2 + ....)^{-n}$ is

The last digit in $7^{300}$ is

Let $[x]$ denote the greatest integer less than or equal to $x$. If for $n \in N$,$(1-x+x^3)^n = \sum_{j=0}^{3n} a_j x^j$,then $\sum_{j=0}^{[\frac{3n}{2}]} a_{2j} + 4 \sum_{j=0}^{[\frac{3n-1}{2}]} a_{2j+1}$ is equal to

The coefficient of $x^4$ in the expansion of $(1+x-x^2-x^3)^{11}$ is