Which of the following statements is correct?

Which is not true about borax?

In the reactions $I$ and $II$,the covalencies of $Be$ and $Al$ in $X$ and $Y$ are respectively:
$I$ $Be(OH)_2 + NaOH \text{ (excess)} \rightarrow X$
$II$ $Al(OH)_3 + NaOH \text{ (excess)} \rightarrow Y$

The element which has the least metallic character is ..........

Borax is actually made of two tetrahedra and two triangular units joined together and should be written as: $Na_2[B_4O_5(OH)_4] \cdot 8H_2O$. Consider the following statements about borax:
$a.$ Each boron atom has four $B-O$ bonds
$b.$ Each boron atom has three $B-O$ bonds
$c.$ Two boron atoms have four $B-O$ bonds while other two have three $B-O$ bonds
$d.$ Each boron atom has one $-OH$ group
Select correct statement$(s)$:

The structure of diborane $(B_2H_6)$ contains :-