What is the product of the reaction between aluminium and aqueous $NaOH$?

$A$ metal $M$ reacts with $N_2$ to form a compound $A$ $(M_3N)$. Heating $A$ at high temperature gives back $M$,and passing $A$ through $H_2O$ produces gas $B$. Gas $B$ turns $CuSO_4$ solution into a deep blue color. What are $A$ and $B$?

$NaOH$ can be transported in the container made up of ?

Metallic magnesium is prepared by

The blue colour of the solution (metal dissolved in liquid ammonia) is due to

Assertion $(A)$: $K$, $Rb$, and $Cs$ form superoxides.
Reason $(R)$: The stability of the superoxides increases from $K$ to $Cs$ due to the decrease in lattice energy.
The correct answer is: