Which ion will not be precipitated by aqueous $(NH_4)_2S$?

Which reagents are used for the identification of Group $IV$ cations?

Addition of sodium thiosulphate solution to a solution of silver nitrate gives $X$ as a white precipitate,which is insoluble in water but soluble in excess thiosulphate solution to give $Y$. On boiling in water,$Y$ gives $Z$. $X$,$Y$,and $Z$ respectively are:

Compound $X$ is tested and the results are shown in the table.

Test	Result
Aqueous $NaOH$ is added,then heated gently.	Gas given off which turns damp red litmus paper blue.
Dilute $HCl$ is added.	Effervescence,gas given off which turns lime water milky and acidified $K_2Cr_2O_7$ paper green.

Which ions are present in compound $X$?

On heating $NaCl + K_2Cr_2O_7 + \text{conc. } H_2SO_4$,the gas evolved is:

Which ion is precipitated by the reagent $NH_4Cl$ and aqueous $NH_3$?