Which of the following has the greatest reducing power?

Which of the following interhalogen compounds does not exist?

$A$ gas reacts with $CaO$,but not with $NaHCO_3$. The gas is

The correct increasing order of oxidizing power is:

Consider the oxy acids $HClO_{n}$ series,where the value of $n$ is $1$ to $4$. Then,the incorrect statement regarding these oxy acids is:

What is the reason for the bleaching action of chlorine?