Which of the following sulphides is yellow in colour?

Statement-$1$: Few drops of $HNO_3$ are added before proceeding to $III^{rd}$ group.
Statement-$2$: For the oxidation of $Fe^{+2} \rightarrow Fe^{+3}$.

Nessler's reagent is used to detect

Sodium nitroprusside when reacts with a solution of $Na_2S$,produces:

$A$ salt reacts with dilute $HCl$ to produce a gas with a pungent smell and yellow crystals. When tested,the salt gives a green flame. With potassium chromate,the salt gives yellow crystals. Therefore,the salt is.......

Identify $A$,$B$ and $C$ in the given reaction sequence.