The brown ring test is used for the detection of which radical?

Which of the statement is incorrect for the given paragraph?
Simple salt $\xrightarrow{\text{Flame test}}$ Golden yellow flame
Simple salt $\xrightarrow[MnO_2]{Conc. H_2SO_4} (X)$ Yellowish green gas
Simple salt $\xrightarrow{AgNO_3} (Z)$ White ppt. (Insoluble in dil. $HNO_3$)
Simple salt $\xrightarrow[Conc. H_2SO_4]{K_2Cr_2O_7} (Y)$ Reddish brown vapour

Given below are two statements:
Statement $I$: Griess-Ilosvay test is used for the detection of nitrite ion,which involves the use of sulphanilic acid and $\alpha$-naphthylamine reagent.
Statement $II$: In the above test,sulphanilic acid is diazotized by the acidified nitrite ion,which on further coupling with $\alpha$-naphthylamine forms an azo-dye.
In the light of the above statements,choose the correct answer from the options given below.

$A$ salt is heated first with dil. $H_2SO_4$ and then with conc. $H_2SO_4$. No reaction takes place. It may be

Assign $A, B, C, D$ from the given type of reaction.
$BaSO_4 \downarrow + dil. HCl$ $(Excess)$ $\longrightarrow$ No reaction

An anion solution gives a white precipitate with $AgNO_3$ solution. The precipitate dissolves in dilute ammonia due to the formation of: