Which of the following is only acidic in nature

Which of the following is formed when aluminium oxide and carbon is strongly heated in dry chlorine gas

$N{a_2}{B_4}{O_7}\xrightarrow{x}{H_3}B{O_3}\xrightarrow{\Delta }{B_2}{O_3}\xrightarrow{y}B$

Here $X, Y$ are respectively

Complete the following chemical equations :

$Z + 3LiAl{H_4} \to X + 3LiF + 3Al{F_3}$

$X + 6{H_2}O \to Y + 6{H_2}$

$3X + 3{O_2}\xrightarrow{\Delta }{B_2}{O_3} + 3{H_2}O$

Boric acid in solid, whereas $BF _3$ is gas at room temperature because of

$H_3BO_3$ $\xrightarrow{{{T_1}}}X\xrightarrow{{{T_2}}}Y\xrightarrow{{red\,hot}}$ $B_2O_3$

if $T_1 < T_2$ then $X$ and $Y$ respectively are