The oxidation state of $I$ in $IPO_4$ is

Which one of the following elements shows both positive and negative oxidation states?

The oxidation state of $+1$ for phosphorus is found in:

Carbon has a valency of $2$ in $CO$ and $4$ in $CO_2$ and $CH_4$. Its valency in acetylene $(C_2H_2)$ is

In view of the signs of $\Delta_{r} G^{\circ}$ for the following reactions:
$PbO_2 + Pb \longrightarrow 2 PbO, \Delta_{r} G^{\circ} < 0$
$SnO_2 + Sn \longrightarrow 2 SnO, \Delta_{r} G^{\circ} > 0$
Which oxidation states are more characteristic for lead and tin?

Assertion : $HClO_4$ is a stronger acid than $HClO_3$.
Reason : Oxidation state of $Cl$ in $HClO_4$ is $+VII$ and in $HClO_3$ is $+V$.