Find the oxidation state of sodium in $Na_2O_2$.

Which one of the following reactions does not involve either oxidation or reduction?

What is the oxidation state of chlorine atom in chloric acid?

When $KMnO_4$ is reduced with oxalic acid in acidic solution,the oxidation number of $Mn$ changes from

State whether the following statements are True or False:
$(1)$ The oxidation number of nitrogen in ammonium chloride $(NH_4Cl)$ is $(-3)$.
$(2)$ The oxidation number of $C$ in methyl chloride $(CH_3Cl)$ is $(-2)$.
$(3)$ In the following reaction,the oxidation number of $Br$ changes from $0$ to $+5$: $Br_2 \to BrO_3^-$.

Consider the following compounds:
$\underline{K}O_2$,$H_2\underline{O}_2$ and $H_2\underline{S}O_4$.
The oxidation states of the underlined elements in them are,respectively,