Identify the $P$ and $Q$ of the following reaction: $P + Q \longrightarrow [B(OH)_4]^{-} + H_3O^{+}$

Boron trifluoride on reaction with lithium aluminium hydride in ether gives $LiF$, $AlF_3$ and $X$. $X$ on reaction with $NH_3$ gives $Y$. $Y$ on further heating gives a compound $Z$. The number of $\sigma$-bonds and $\pi$-bonds in $Z$ are $x$ and $y$ respectively. $(x+y)$ is equal to

Which one is a pseudo alum?

Boron halides behave as Lewis acids because of their nature.

An aqueous solution of borax is

Which pair of oxides is acidic in nature?