The oxidation state of $I$ in $H_4IO_6^-$ is

What is the oxidation state of $Fe$ in $Fe_3O_4$?

What is the oxidation number of $N$ in $NH_2-NH_2$?

The oxidation state of the oxygen atom in potassium superoxide is:

What is the change in oxidation number of $Cr$ in the following redox reaction?
$3H_2O_2(aq) + Cr_2O_7^{2-}(aq) + 8H^+(aq) \rightarrow 3O_2(g) + 2Cr^{3+}(aq) + 7H_2O(l)$

The equivalent weight of potassium permanganate in an alkaline medium is........