What are the compounds formed when white phosphorus is dissolved in boiling $NaOH$ solution in an inert atmosphere?

Which gas is evolved when ammonium dichromate is heated?

In group $-15$,as we move from $N$ to $Bi$,the $M_2O_3$ type oxides become ...... .

$P_2O_3 + H_2O \rightarrow X$
$Red \ P_4 + \text{alkali} \rightarrow Y$
$X$ and $Y$ are oxoacids of phosphorus. The number of $P-OH$ bonds in $X$ and $Y$ respectively is:

Strong reducing behaviour of $H_3PO_2$ is due to

The nitrogen-containing compound produced in the reaction of $HNO_3$ with $P_4O_{10}$:
$(A)$ can also be prepared by the reaction of $P_4$ and $HNO_3$
$(B)$ is diamagnetic
$(C)$ contains one $N-N$ bond
$(D)$ reacts with $Na$ metal producing a brown gas