Precipitate of group $IV$ cations takes place when $H_2S$ is

$A$ 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:

Assign $A$,$B$,$C$,$D$ from the given type of reaction.
$AlCl_3 + Na_3PO_4 \longrightarrow AlPO_4 \downarrow$

An aqueous solution of a mixture of two inorganic salts,when treated with dilute $HCl$,gave a precipitate $(P)$ and a filtrate $(Q)$. The precipitate $P$ was found to dissolve in hot water. The filtrate $(Q)$ remained unchanged when treated with $H_2S$ in a dilute mineral acid medium. However,it gave a precipitate $(R)$ with $H_2S$ in an ammoniacal medium. The precipitate $R$ gave a coloured solution $(S)$ when treated with $H_2O_2$ in an aqueous $NaOH$ medium.
$1.$ The precipitate $P$ contains
$(A)$ $Pb^{2+}$ $(B)$ $Hg_2^{2+}$ $(C)$ $Ag^{+}$ $(D)$ $Hg^{2+}$
$2.$ The coloured solution $S$ contains
$(A)$ $Fe_2(SO_4)_3$ $(B)$ $CuSO_4$ $(C)$ $ZnSO_4$ $(D)$ $Na_2CrO_4$

To an aqueous solution containing ions such as $Al^{3+}, Zn^{2+}, Ca^{2+}, Fe^{3+}, Ni^{2+}, Ba^{2+}$ and $Cu^{2+}$,concentrated $HCl$ was added,followed by $H_{2}S$. The total number of cations precipitated during this reaction is/are:

An aqueous solution of an inorganic salt on treatment with $HCl$ gives a white precipitate. This solution contains