Which effect is observed when the pressure of a gas increases?

$A$ gas occupies $10 \ L$ at $STP$. Which of the following conditions will result in the same volume?

Three flasks of equal volumes contain $CH_4$,$CO_2$,and $Cl_2$ gases respectively. They will contain equal number of molecules if

The compressibility factor for an ideal gas is

At $273 \, K$ temperature and $1 \, bar$ pressure,if the volume of a gas increases by $20 \%$,what temperature is required assuming pressure remains constant (in $, K$)?

$A$ $100 \ L$ cylinder containing $H_2$ exerted a pressure of $4 \ atm$ at $300 \ K$. It was accidentally opened and some $H_2$ escaped. When it was closed,it exerted a pressure of $3 \ atm$ at $300 \ K$. The number of moles of $H_2$ remaining in the cylinder is equal to (Assume $H_2$ as an ideal gas; $R=$ gas constant)