Oxidation number of oxygen in potassium superoxide $(KO_2)$ is

In the reaction of potassium dichromate,potassium chloride and sulfuric acid (conc.),the oxidation state of the chromium in the product is $(+)$ . . . . . . .

Find out the oxidation number of chlorine in the following compounds and arrange them in increasing order of oxidation number of chlorine.
$NaClO_4, NaClO_3, NaClO, KClO_2, Cl_2O_7, ClO_3, Cl_2O, NaCl, Cl_2, ClO_2$.
Which oxidation state is not present in any of the above compounds?

When $K_2Cr_2O_7$ is converted to $K_2CrO_4$,the change in the oxidation state of chromium is

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 $+5$: $Br_2 \to BrO_3^-$.

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