Which of the following halogens is most easily reduced?

When cold $NaOH$ reacts with $Cl_2$,which of the following is formed?

The number of halogen$(s)$ forming halic $(V)$ acid is ..... .

When a brown compound of manganese $(A)$ is treated with $HCl$,it gives a gas $(B)$. The gas,when taken in excess,reacts with $NH_{3}$ to give an explosive compound $(C)$. Identify compounds $A$,$B$,and $C$.

What is the correct order of bond dissociation energy for the given halogens?

$A$ mixture of concentrated $HCl$ and $HNO_3$ in a $3:1$ ratio contains ..........