A monoatomic ideal gas undergoes a series of processes $1-2-3-4$ on $T-P$ diagram as shown.Choose the correct statement(s)

$1-2$ Isothermal compression.

$2-3$ isochoric cooling.

during $3-4$

$$\begin{gathered} T=aP+b \\ PV=nRT \\ V=\frac{nR(aP+b)}{\rho }=nR\left(a+\frac{b}{P}\right) \\ P\uparrow \Rightarrow v\downarrow \Rightarrow W=-ve \\ During 3-4 , as temperature is increa\sin g , internal energy is also increa\sin g . \end{gathered}$$