Midpoint of $\left(-2,-1\right)$ & $\left(\mathrm{4,3}\right)$ is $\left(\mathrm{1,1}\right)$
Midpoint of $\left(\mathrm{1,0}\right)$ & $\left(\mathrm{1,2}\right)$ is $\left(\mathrm{1,1}\right)$
Hence, $\left(-2,-1\right),\left(\mathrm{1,0}\right),\left(\mathrm{4,3}\right)$ and $\left(\mathrm{1,2}\right)$ are the vertices of a parallelogram.
Now, the distance between $\left(-2,-1\right)$ and $\left(\mathrm{4,3}\right)$ is $\sqrt{52}$ and the distance between $\left(\mathrm{1,0}\right)$ & $\left(\mathrm{1,2}\right)$ is $2$
Because $\sqrt{52}\ne 2$, hence, points do not form a rectangle