Which of the following does not exist in free form?

The chemical name of borax is

Write balanced chemical equations for the following reactions:
$(i)$ $BF_3 + LiH \rightarrow$
$(ii)$ $B_2H_6 + H_2O \rightarrow$
$(iii)$ $NaH + B_2H_6 \rightarrow$
$(iv)$ $H_3BO_3 \xrightarrow{\Delta}$
$(v)$ $Al + NaOH \rightarrow$
$(vi)$ $B_2H_6 + NH_3 \rightarrow$

Which of the following statements is not true?

$A$ and $B$ are formed when borax is dissolved in water. $C$ and $B$ are formed when borax is reacted with aqueous $HCl$ solution. What are $A$ and $C$ respectively?

$AlCl_3$ fumes in moist air because.......