Which of the following processes is reversible?

Two cylinders $A$ and $B$ of equal capacity are connected to each other via a stop cock. Cylinder $A$ contains an ideal gas at standard temperature and pressure. Cylinder $B$ is completely evacuated. The entire system is thermally insulated. The stop cock is suddenly opened. The process is:

$A$ thermally insulated container is divided into two parts by a screen. In one part,an ideal gas is filled at pressure $P$ and temperature $T$. The second part is a vacuum. If a small hole is now created in the screen,the temperature of the gas will:

Is the rusting of iron a reversible process? Why?

If a cylinder containing a gas at high pressure explodes,the gas undergoes

$A$ process can be reversible if