What is the oxidation number of $S$ in $SO_4^{2-}$?

Given below are two statements.
Statement $I$ : In $H_2O_2$, each oxygen atom is assigned an oxidation number of $-1$, and in $RbO_2$, each oxygen atom is assigned an oxidation number of $-\frac{1}{2}$.
Statement $II$ : The representation of $HAuCl_4$ and $MnO_2$ in Stock notation is $HAu(III)Cl_4$ and $Mn(IV)O_2$ respectively.
Examine the above statements and choose the correct answer.

Oxidation states of $P$ in $H_{4}P_{2}O_{5}, H_{4}P_{2}O_{6}, H_{4}P_{2}O_{7}$ are respectively:

What are the oxidation numbers of $S$ atoms in $S_4O_6^{2-}$?

Write the oxidation number of oxygen in $KO_{3}$ and $Na_{2}O_{2}$.

The oxidation number of phosphorus in $Ba(H_2PO_2)_2$ is