Nessler's reagent is used to detect

Among $Fe^{3+}$,$Pb^{2+}$,$Cu^{2+}$,and $Mn^{2+}$,identify the one that gets precipitated out while passing $H_2S$ gas in the presence of $NH_4OH$ as a group reagent. The highest possible oxidation state of the corresponding metal is:

$(T)$ imparts violet colour $\xrightarrow{compd.\,(U) + conc.\,H_2SO_4}$ $(V)$ Red gas $\xrightarrow{NaOH + AgNO_3}$ $(W)$ Red ppt. $\xrightarrow{NH_3\,soln.}$ $(X)$
$(W)$ Red ppt. $\xrightarrow{dil.\,HCl}$ $(Y)$ white ppt.
$(U)$ $\xrightarrow[\Delta]{NaOH}$ $(Z)$ gas (gives white fumes with $HCl$)?
$(T)$ sublimes on heating
Identify $(T)$ to $(Z).$

Among $PbS$,$CuS$,$HgS$,$MnS$,$Ag_2S$,$NiS$,$CoS$,$Bi_2S_3$,and $SnS_2$,the total number of black coloured sulphides is

$Pb(CH_3COO)_2$ gives a precipitate of which color with $H_2S$?

Concentrated aqueous $NaOH$ can separate a mixture of