Which hydride among the following is the strongest reducing agent?

Which among the following oxoacids of phosphorus will have $P-O-P$ bonds?
$I$. $H_4P_2O_5$
$II$. $H_4P_2O_6$
$III$. $H_4P_2O_7$
$IV$. $(HPO_3)_3$

At what temperature is white phosphorus heated to form $\beta$-black phosphorus (in $K$)?

The laughing gas is

Nitric acid oxidises phosphorus to

When a brown compound of manganese $(A)$ is treated with $HCl$,it gives a gas $(B)$. The gas $(B)$ taken in excess reacts with $NH_3$ to give an explosive compound $(C)$. The compounds $A$,$B$ and $C$ are: