Which one of the following has the highest oxidation number of iodine?

$1 \ mol$ of compound $N_2H_4$ loses $10 \ mol$ of electrons to form a new compound $Y$. Assuming all nitrogen atoms are present in compound $Y$,what is the oxidation state of $N$ in compound $Y$?

In acidic medium,$H_2O_2$ changes $Cr_2O_7^{2-}$ to $CrO_5$ which has two peroxy linkages. The oxidation state of $Cr$ in $CrO_5$ is

The oxidation states of sulfur atoms and the number of $S-OH$ bonds in Peroxydisulfuric acid are respectively:

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

What is the oxidation number of $Li$ in $Li_2O$?