Which of the following does not exist in free form?

Identify the correct statements from the following :
$I$. $Ga_2O_3$ is an amphoteric oxide.
$II$. The dimer of aluminium chloride has three $Al-Cl-Al$ bridge bonds.
$III$. Boron is a very hard refractory solid of high melting temperature.

Which of the following compounds are formed when boron trichloride is treated with water?

Borax in its crystal structure possesses:

Which of the following chlorides does not react with $PCl_5$ on heating?

Complete the following chemical equations:
$4BF_{3} + 3LiAlH_{4} \to 2B_{2}H_{6} (X) + 3LiF + 3AlF_{3}$
$B_{2}H_{6} (X) + 6H_{2}O \to 2H_{3}BO_{3} (Y) + 6H_{2}$
$B_{2}H_{6} (X) + 3O_{2} \xrightarrow{\Delta} B_{2}O_{3} + 3H_{2}O$