Which one of the following anions is not easily removed from aqueous solutions by precipitation?

To an inorganic mixture,dilute $H_2SO_4$ is added in the cold; a colourless,odourless gas is evolved. The mixture contains:

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

Which of the following substances releases $SO_2$ gas upon reaction with dilute $H_2SO_4$?

When $BaCl_2$ is added to a clear solution of a compound $(X)$,a heavy white precipitate is formed which does not dissolve in $dil. HCl$. What is the compound $(X)$?

In the chromyl chloride test,the reagent used is