$A$ gas deviates most from ideal behavior when it is subjected to

Gases deviate from ideal behaviour at high pressures because the gas molecules

What will the van der Waals equation be at high temperature and low pressure?

When is deviation more in the behaviour of a gas from the ideal gas equation $PV = nRT$?

$a$ and $b$ are van der Waals constants for gases. Chlorine is more easily liquefied than ethane because

For real gases,the relation between $p$,$V$,and $T$ is given by the van der Waals equation:
$(p + \frac{an^2}{V^2})(V - nb) = nRT$
Where $a$ and $b$ are van der Waals constants,$nb$ is approximately equal to the total volume of the molecules of a gas,and $a$ is the measure of the magnitude of intermolecular attraction.
$(i)$ Arrange the following gases in the increasing order of $b$. Give reason: $O_2, CO_2, H_2, He$
$(ii)$ Arrange the following gases in the decreasing order of magnitude of $a$. Give reason: $CH_4, O_2, H_2$