Which of the following metals produces hydrogen gas when heated with hot concentrated alkali?

When sodium is dissolved in liquid ammonia,a deep blue coloured solution is obtained. This colour of the solution is due to:

Identify the correct statements from the following.
$A$: Alkali metals are strong reducing agents.
$B$: $KO_2$ is a diamagnetic oxide.
$C$: Hydration enthalpy of $Li^{+}$ is the highest among alkali metal ions.

When $CO_2$ gas is passed through an aqueous solution of $Na_2CO_3$,what is formed?

Calcium on heating in $N_2$ yields an ionic compound $A$, which reacts with water to give $Ca(OH)_2$ and a gas $B$. Identify $A$ and $B$.

Consider the following reactions:
$Cs + O_2 \text{ (excess)} \rightarrow X$
$Na + O_2 \rightarrow Y$
Identify the correct statement about $X$ and $Y$.