Which of the following is the correct order of acidic strength?

$HClO_4$ is a stronger acid than $H_2SO_4$ due to which of the following reasons?
$1$. Oxidation state of $Cl$ in $HClO_4$ is $+7$ and that of $S$ in $H_2SO_4$ is $+6$.
$2$. $Cl$ is more electronegative than $S$.
$3$. $HClO_4$ is monobasic,whereas $H_2SO_4$ is dibasic.
$4$. $ClO_3$ part of $HClO_4$ can break $O-H$ bond more easily to liberate a proton than $SO_3$ part in $H_2SO_4$.

Which of the following gases can displace all other gases from a mixture?

If $X(OH) > Y(OH)$ (acidic strength) and $X$ and $Y$ both belong to the same group,then select the $CORRECT$ statement:

The elements in which $s$ and $p$-orbitals are present are known as:

How many elements in the periodic table are gases? Provide their positions in the periodic table.