White phosphorus contains

$NH_3$ is $NOT$ used in which of the following?

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

Silver nitrate is prepared by the reaction of:

Ammonia with excess of $Cl_2$ forms:

On heating,lead$(II)$ nitrate gives a brown gas $(A).$ The gas $(A)$ on cooling changes to a colourless solid/liquid $(B).$ $(B)$ on heating with $NO$ changes to a blue solid $(C).$ The oxidation number of nitrogen in solid $(C)$ is :