The oxidation number of fluorine in $F_2O$ is

Which one is an incorrect statement?

What is the oxidation state of iodine in $I_2Cl_6$?

The oxidation states of $P$ in $PO_4^{3-}$,$S$ in $SO_4^{2-}$,and $Cr$ in $Cr_2O_7^{2-}$ are respectively:

$2.5 \ mol$ of hydrazine $(N_2H_4)$ loses $25 \ mol$ of electrons to form a new compound $X$. Assuming all lost electrons are contained in the new compound,what is the oxidation state of nitrogen in compound $X$?

The oxidation number of carbon in $H_2C_2O_4$ is: