Which of the following salts gives a white precipitate with $AgNO_3$ and dilute $H_2SO_4$,and also gives a green flame test?

In the group analysis of cations, $Ba^{2+}$ and $Ca^{2+}$ are precipitated respectively as

$A$ light greenish coloured salt was soluble in water. On passing $H_2S$ into the solution,a black precipitate was obtained which dissolved readily in $HCl$. The metal ion present is:

$A$ solution is prepared by mixing a concentrated solution of $Co(NO_3)_2$ with a concentrated solution of $NaNO_2$ in $50\%$ acetic acid. $A$ solution of a salt containing metal $M$ is added to the mixture, and a yellow precipitate is formed. Metal $M$ is:

Aqueous solution of $FeSO_4$ does not produce a precipitate with:

Assign $A, B, C, D$ from the given type of reaction:
$2KCN + Pb(NO_3)_2 \longrightarrow Pb(CN)_2 \downarrow + 2KNO_3$