Which of the following gives a precipitate with $Pb(NO_3)_2$ but not with $Ba(NO_3)_2$?

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

$A$ solution of a salt in dilute sulphuric acid imparts a deep blue colour with starch-iodine solution; it confirms the presence of which of the following?

Which anion of a sodium salt gives a white precipitate upon heating with a magnesium salt?

Which of the following ions will not give a precipitate with $AgNO_3$?

$A$ brown ring appears in the test for