Which of the following chemical substances undergoes self-oxidation and self-reduction during the same reaction?

Which of the following acts as both an oxidizing and a reducing agent?

In the following reaction,assign the oxidation state for the underlined atom in the product of complete hydrolysis at $R.T.$:
$\underline{Cl}O_3 + H_2O \longrightarrow HClO_3 + HClO_4$

The species given below that does $NOT$ show disproportionation reaction is :

The reaction occurring when $Cl_2$ gas is passed through a concentrated solution of $NaOH$ is called .....

In the following reaction,assign the state for the underlined atom in the products of complete hydrolysis at $R.T.$: $\underline{N}_2O_4 + H_2O \longrightarrow HNO_3 + HNO_2$