Among the members of $V$ $A$ group ($N$,$P$,$As$,$Sb$,and $Bi$),which of the following properties shows an increase as we go down from nitrogen to bismuth?

Which element among the following forms $P \pi-P \pi$ multiple bonds?

Which element from group $15$ ($V$ group) forms the most basic compound with hydrogen?

Given below are two statements:
Statement $I$: The $N-N$ single bond is weaker and longer than the $P-P$ single bond.
Statement $II$: Compounds of group $15$ elements in $+3$ oxidation state readily undergo disproportionation reactions.
In the light of the above statements,choose the correct answer from the options given below:

Extra pure $N_2$ can be obtained by heating

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