Which of the following compounds of boron is the hardest?

In the reaction $B_2H_6 + 2KOH + 2X \to 2Y + 6H_2$,$X$ and $Y$ are respectively

Which one is a pseudo alum?

The incorrect statement regarding the above reactions is:
$Al \xrightarrow{HCl(aq.)} 'X' + \text{Gas } 'P'$
$Al \xrightarrow{NaOH(aq.) + H_2O} 'Y' + \text{Gas } 'Q'$

The correct order of Lewis acidity for $BX_3$ is:

Colemanite is