Which compound from the following contains iodine with the highest oxidation number?

If a metal ion $M^{3+}$ loses three more electrons,what will be its final oxidation number?

What are the oxidation numbers of the underlined elements in each of the following and how do you rationalize your results?
$(1)$ $K\underline{I_3}$
$(2)$ $H_2\underline{S_4}O_6$
$(3)$ $\underline{Fe_3}O_4$
$(4)$ $\underline{C}H_3\underline{C}H_2OH$
$(5)$ $\underline{C}H_3\underline{C}OOH$

What is the oxidation state of oxygen in $OF_2$?

What is the oxidation state of $S$ in $SO_4^{2-}$?

Oxidation number of $P$ in $Mg_2P_2O_7$ is