Which of the following statement$(s)$ is/are true? "Internal energy of an ideal gas ..........."

An ideal gas undergoes four different processes from the same initial state as shown in the figure below. Those processes are adiabatic,isothermal,isobaric and isochoric. The curve which represents the adiabatic process among $1, 2, 3$ and $4$ is

$A$ gas expands such that its initial and final temperatures are equal. Also,the process followed by the gas traces a straight line on the $P-V$ diagram:

The $P-V$ diagram shown represents the thermodynamic cycle of an engine operating with an ideal monatomic gas. The amount of heat extracted from the source in a single cycle is:

Two cylinders $A$ and $B$ fitted with pistons contain equal amounts of an ideal diatomic gas at $300 \ K$. The piston of $A$ is free to move,while that of $B$ is held fixed. The same amount of heat is given to the gas in each cylinder. If the rise in temperature of the gas in $A$ is $30 \ K$,then the rise in temperature of the gas in $B$ is ..... $K$.

In thermodynamic processes, which of the following statements is not true?