Which element of group $13$ does not show the group valency in its compounds?

The Lewis acid strength of $BBr_3$,$BCl_3$,and $BF_3$ is in the order:

Hydrated $AlCl_3$ is used as :

Inorganic graphite is

$A$ certain salt $X$ gives the following results:
$(i)$ Its aqueous solution is alkaline to litmus.
$(ii)$ It swells up to a glassy material $Y$ on strong heating.
$(iii)$ When conc. $H_{2}SO_{4}$ is added to a hot solution of $X,$ white crystals of an acid $Z$ separate out.
Write equations for all the above reactions and identify $X, Y,$ and $Z$.

Which of the following structures is similar to graphite?