Which of the following is the common name for peroxymonosulfuric acid?

Assertion $(A)$: The colour of old lead paintings can be restored by washing them with a dilute solution of $H_2O_2$.
Reason $(R)$: Hydrogen peroxide reduces $PbS$ to $Pb$.

$Hydrogen$ $peroxide$ is reduced by:

The decomposition of hydrogen peroxide is an example of

Fill in the blanks:
$(1)$ $H_2O_2$ acts as an antiseptic, then it is known as ......... in the market.
$(2)$ Cation exchange resin is a ......... group containing organic molecule.
$(3)$ The ionic radius of $H^+$ ions and that of other ions is ......... $pm$ and ......... $pm$ respectively.
$(4)$ ......... group elements give salt-like hydrides.

The molecular mass of hydrogen peroxide is $34$. Its unit is .....