Which pair of elements can form multiple bonds with itself and oxygen?

Nitrolim is

It is observed that $Pb^{2+}$ is more stable than $Pb^{4+}$, while $Sn^{2+}$ is less stable than $Sn^{4+}$. Consider the following reactions:
$PbO_{2} + Pb \rightarrow 2PbO; \Delta_{r}G^{\circ} (1)$
$SnO_{2} + Sn \rightarrow 2SnO; \Delta_{r}G^{\circ} (2)$
Identify the correct set from the following.

In the following reaction,identify the nature of the product formed by the complete hydrolysis of the underlined atom at $R.T.$:
$\underline{S}O_2 + H_2O \longrightarrow H_2SO_3$

In which of the following commercial processes is a catalyst not used?

Which of the following has the lowest melting point?