Which of the following sets represents the alkali metals?

$X$ $\xrightarrow{N_2, \Delta} Y$ $\xrightarrow{H_2O} Z$ (colourless gas) $\xrightarrow{CuSO_4} T$ (blue colour)
Then,substances $Y$ and $T$ are

When carbon monoxide is passed over solid caustic soda heated to $200^{\circ} C$,it forms

Based on lattice energy and other considerations,which one of the following alkali metal chlorides is expected to have the highest melting point?

In $LiAlH_4$,metal $Al$ is present in

Give the biological importance of the sodium ion $(Na^+)$.