Hydrogen peroxide acts both as an oxidising and as a reducing agent depending upon the nature of the reacting species. In which of the following cases $H_2O_2$ acts as a reducing agent in acidic medium?

Decolourisation of acidified potassium permanganate occurs when $H_2O_2$ is added to it,this is due to

The decomposition of hydrogen peroxide is an example of

Assertion $:$ Amount of $H_2O_2$ in a sample can be determined by treating $H_2O_2$ solution with $KI$ and followed by titration of liberated $I_2$ with sodium thiosulphate.
Reason $:$ In this titration,an intense blue colour appears which disappears at the end point.

The correct statements among the following are
$i$. Saline hydrides produce $H_2$ gas when reacted with water
$ii$. Presently $\sim 77 \%$ of the industrial dihydrogen is produced from coal
$iii$. Commercially marketed $H_2O_2$ contains $3 \% H_2O_2$

$1 \ mL$ of $H_2O_2$ solution gives $10 \ mL$ of $O_2$ at $NTP$. It is ................ vol. $H_2O_2$.