According the van der Waal's theory of non-ideal gases, which of the following statement is/are correct?

${\mathrm{H}}_2$ and He are impossible to liquefy at room temperature.

For ${\mathrm{NH}}_3$ , Z decreases more rapidly on increasing pressure than the methane in lower pressure region

In the low pressure region, Z decreases on increasing pressure, ${\mathrm{H}}_2$ and He are exception to that.

In the high pressure region, Z increases with increasing pressure, ${\mathrm{H}}_2$ and He are exception to that