Oxidation number of oxygen in ozone $(O_3)$ is

The difference in oxidation state of chromium in chromate and dichromate salts is $....$ .

In which compound is the oxidation state of nitrogen $-1$?

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.

Sulphur in $+3$ oxidation state is present in

The oxidation state of each oxygen atom in $Na_{2}O_{2}$ is