Which of the following is sparingly soluble in cold water and fairly soluble in hot water?

Nessler's reagent is

$A$ (Orange color compound) $\xrightarrow{(B) + \text{conc. } H_2SO_4}$ $C$ (Red gas) $\xrightarrow{NaOH + AgNO_3}$ $D$ (Red ppt.) $\xrightarrow{\text{NH}_3 \text{ solution}}$ Yellow solution.
$B$ $\xrightarrow[\Delta]{NaOH}$ $F \uparrow$ (Gives white fumes with $HCl$).
Identify $B$ and $F$ respectively :-

Lead sulphate is soluble in:

$H_2S$ gas is passed through an acidified solution containing $Ag^+$,$Cu^{2+}$,and $Zn^{2+}$ ions. Which of these will form a precipitate?

$A$ compound is soluble in water. If ammonia is added,a red precipitate appears which is soluble in dilute $HCl$. The compound contains: