What is the product formed when sodium reacts with an excess of oxygen/air?

When sodium is burnt in moist air,the final product will be:

$A$ 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 $B$?

$A$ metal $X$ on heating in a stream of nitrogen gas gives $Y$. $Y$ on reaction with $H_2O$ gives a colorless gas which turns $CuSO_4$ solution blue. What is $Y$?

$NaOH$ is prepared by the method:

The essential constituent of an amalgam is: