Which of the following compounds is formed by the addition of a mineral acid to an aqueous solution of borax?

$Na_2B_4O_7 \cdot 10H_2O \xrightarrow{\Delta} X + NaBO_2 + H_2O$
$X + Cr_2O_3 \xrightarrow{\Delta} Y$ (Green coloured)
$X$ and $Y$ are

Consider the following statements for diborane $(B_2H_6)$:
$1.$ Boron is approximately $sp^3$ hybridized.
$2.$ $B-H-B$ angle is $180^{\circ}$.
$3.$ There are two terminal $B-H$ bonds for each boron atom.
$4.$ There are only $12$ bonding electrons available.
Which of these statements are correct?

When orthoboric acid is heated,the residue left is ...

The correct statements from the following are $:$
$(A)$ $Tl^{3+}$ is a powerful oxidising agent
$(B)$ $Al^{3+}$ does not get reduced easily
$(C)$ Both $Al^{3+}$ and $Tl^{3+}$ are very stable in solution
$(D)$ $Tl^{+}$ is more stable than $Tl^{3+}$
$(E)$ $Al^{3+}$ and $Tl^{+}$ are highly stable
Choose the correct answer from the options given below $:$

Two elements $X$ and $Y$ react with highly electropositive metals to form binary compounds,which upon hydrolysis yield borane and silane,respectively. What are $X$ and $Y$?