Group $2$ hydrides with significant covalent character is/are:

What are $X$,$Y$ and $Z$ in the following reactions?
$CaCO_3 \stackrel{\Delta}{\rightleftharpoons} CO_2 + X$
$X + H_2O \longrightarrow Y$
$Y + Cl_2 \longrightarrow Z$

Which of the following statements is incorrect?

The element with electronic configuration $1s^2, 2s^2 2p^6, 3s^2$ would be

$ZnO$ when heated with $BaO$ at $1100\,^{\circ}C$ gives a compound. Identify the compound.

Identify the amphoteric oxide from the following.