Nitric acid oxidises phosphorus to

Which acid is formed by $P_2O_3$?

$A$ metal $(X)$ dissolves in both dilute $HCl$ and dilute $NaOH$ to liberate $H_2$ gas. Addition of $NH_4Cl$ and excess $NH_4OH$ to an $HCl$ solution of $(X)$ produces $(Y)$ as a precipitate. $(Y)$ is also produced by adding $NH_4Cl$ to the $NaOH$ solution of $(X)$. The species $(X)$ and $(Y)$,respectively,are:

The acidic character of the group-$15$ elements' oxides in increasing order is:

$A + H_2O \to B + HCl$
$B + H_2O \to C + HCl$
Compound $(A), (B)$ and $(C)$ will be respectively

Which element of the $13^{th}$ group does not show the group oxidation state in its compounds?