Consider the set of matrices
$$G=\left\{\left(\begin{array}{ll}s & b \\ 0 & 1\end{array}\right): b \in \mathbb{Z}, s \in\{-1,+1\}\right\}$$
Then which of the following is true?
1. $G$ forms a group under addition
2. $G$ forms an abelian group under multiplication
3. Every element in $G$ is diagonalisable over $\mathbb{C}$
4. $G$ is a finitely generated group under multiplication