Which one of the following is fluorspar?

Which of the following will not give a flame test?

When $MgCl_2 \cdot 6H_2O$ is strongly heated,then it forms

$A$ pair of amphoteric oxides is

Amongst the following hydroxides,the one which has the highest value of $K_{sp}$ at ordinary temperature is

Heating a solid compound $X$ produces $CO_2$ gas and a residue. Adding water to this residue produces compound $Y$. Passing excess $CO_2$ gas through a solution of $Y$ produces a clear solution $Z$. Boiling $Z$ regenerates compound $X$. What is compound $X$?