Which of the following statement is/are correct for $H_2O_2$?

In which of the following reactions,hydrogen peroxide acts as an oxidizing agent?

$H_2O_2$ is always stored in black bottles because

The correct statements from the following are:
$i$. $Ca(OH)_2$ is used in Clark's method of removal of temporary hardness of water.
$ii$. $100 \ mL$ of $10$ vol $H_2O_2$ on complete decomposition liberates $1 \ L$ of oxygen at $STP$.
$iii$. Urea can be added to the solution of $H_2O_2$ as stabilizer.

Calculate the volume strength of $1.5 \ N \ H_2O_2$.

$KO_2$ reacts with water to form $A$,$B$ and $C$. $B$ forms $C$ when it reacts with iodine in basic medium. What are $B$ and $C$ respectively?