Identify the incorrect statement about silica $(SiO_2)$.

Identify the correct statements from the following.
$i$. Melting points and boiling points of group $13$ elements are much higher than those of corresponding group $14$ elements.
$ii$. $SiO$ only exists at high temperatures.
$iii$. $PbI_4$ does not exist.
$iv$. Buckminster fullerene contains twelve $6$-membered carbon rings and twenty $5$-membered carbon rings.

An oxide of an element is a gas and dissolves in water to give an acidic solution. The element belongs to:

Which of the following halides is least stable and has doubtful existence?

The correct increasing order of extent of hydrolysis is

The catenation tendency of $C, Si$ and $Ge$ is in the order $Ge < Si < C$. The bond energies (in $kJ \ mol^{-1}$) of $C-C, Si-Si$ and $Ge-Ge$ bonds,respectively,are: