What precipitate is formed when $SnCl_2$ is added to $HgCl_2$?

Sometimes yellow turbidity appears on passing $H_2S$ gas even in the absence of the second group radicals. This happens because

When $MgSO_4$ is treated with $NH_4OH$ and $Na_2HPO_4$,a white crystalline solid is formed. What is its formula?

The group reagent $NH_4Cl_{(s)}$ and aqueous $NH_3$ will precipitate which of the following ions?

Which reagents are used for the identification of Group $IV$ cations?

Salt $X$ is:
$X \text{ (Colourless salt)}$ $\xrightarrow[\Delta]{NaOH} Y$ $\xrightarrow{HCl} \text{White fumes}$
$X \text{ (Colourless salt)}$ $\xrightarrow{CaCl_2} Z \text{ (White ppts.)}$ $\xrightarrow{KMnO_4} \text{Colourless solution}$