What is the oxidation number of $P$ in $Ba(H_2PO_2)_2$?

What is the oxidation number of the oxygen atom in the $O_2^{2-}$ ion?

The oxidation number of sulphur in $H_2S$ is

In acidic medium,$H_2O_2$ changes $Cr_2O_7^{2-}$ to $CrO_5$ which has two $(-O-O-)$ bonds. Oxidation state of $Cr$ in $CrO_5$ is

Suggest a list of substances where carbon can exhibit oxidation states from $-4$ to $+4$ and nitrogen from $-3$ to $+5$.

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.