Which of the following molecules can act as an oxidizing as well as a reducing agent?

In the following reaction,identify the nature of the product formed by the complete hydrolysis of the underlined atom at $R.T.$:
${H_2}{\underline{S}}_2{O_8} + {H_2}O \longrightarrow {H_2}S{O_4} + {H_2}O_2$

Which one of the following chemical agents is not used for the dry-cleaning of clothes?

Two litres of $15$ volume solution of $H_2O_2$ on complete decomposition liberated $x$ litres of $O_2$ at $STP$. What is the value of $x$ (in litres)?

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.

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