What is the product obtained when orthophosphoric acid $(H_3PO_4)$ is heated to a high temperature?

Choose the correct statement$(s)$ among the following.
$A$. $SnCl_2 \cdot 2 H_2O$ is a reducing agent.
$B$. $SnO_2$ reacts with $KOH$ to form $K_2[Sn(OH)_6]$.
$C$. $A$ solution of $PbCl_2$ in $HCl$ contains $Pb^{2+}$ and $Cl^{-}$ ions.
$D$. The reaction of $Pb_3O_4$ with hot dilute nitric acid to give $PbO_2$ is a redox reaction.

During which of the following processes is phosphine $(PH_3)$ $NOT$ obtained?

$A$ 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:

$HNO_3 + P_4O_{10} \rightarrow HPO_3 + A$; the product $A$ is

Which of the following is the incorrect order?