The reversible expansion of an ideal gas under adiabatic and isothermal conditions is shown in the figure. Which of the following statement is incorrect?

In an isothermal process, temperature is constant $T_2=T_1$

Area under P-V graph is more in isothermal $W_{isothermal}>W_{adiabatic}\Rightarrow Now\Delta U_{isothermal}=0$

In adiabatic $T_1{V_1}^{\gamma -1}=T_3{V_3}^{\gamma -1}\Rightarrow \frac{T_2}{T_1}={\left(\frac{V_1}{V_3}\right)}^{\gamma -1}. T_3<T_1$ hence internal energy decreases $\Delta U_{isothermal}>\Delta U_{adiabatic}$