$\left[\begin{array}{cccc}1&0&0&0\\0&1&0&0\\0&0&1&0\\0&0& 0&1\end{array}\right]$
2. What happens when you take a real number and multiply it by that matrix? You are just gonna get all scalar matrices $\lambda I_4$ for $\lambda \in \mathbb{F}$ where $\mathbb{F}$ is the field over which the matrix is, I assume probably just the real numbers.