How does $H_2O_2$ behave as a bleaching agent?

Rohan heard that instructions were given to the laboratory attendant to store a particular chemical,i.e.,keep it in the dark room,add some urea in it,and keep it away from dust. This chemical acts as an oxidising as well as a reducing agent in both acidic and alkaline media. This chemical is important for use in the pollution control treatment of domestic and industrial effluents.
$(i)$ Write the name of this compound.
$(ii)$ Explain why such precautions are taken for storing this chemical.

$1 \ mL$ of "$x$ volume" $H_2O_2$ solution on heating gives $20 \ mL$ of oxygen gas at $STP$. The $(w/v) \%$ corresponding to "$x$ volume" of $H_2O_2$ is

Which of the following statements is correct?

$A$ commercial sample of $H_2O_2$ marked as $100$ volume hydrogen peroxide means:

How many $mL$ of perhydrol is required to produce sufficient oxygen which can be used to completely convert $2 \ L$ of $SO_2$ gas to $SO_3$ gas (in $mL$)?