\((3)\) One to \(-M\) of \(NO_2\) and onho effect it is weak base.
\((2)\) Strong base lone pair is not involved in resonance.
(1) (2) $CH_3CH_2NH_2$
(3) $(CH_3)_2NH$ (4) $\begin{array}{*{20}{c}}
O \\
{|\,|} \\
{C{H_3} - C - N{H_2}}
\end{array}$