The acid which forms two series of salts is

$A$ compound $X$,of boron reacts with $NH_3$ on heating to give another compound $Y$,which is called inorganic benzene. The compound $X$ can be prepared by treating $BF_3$ with lithium aluminium hydride. The compounds $X$ and $Y$ are represented by the formulas.

Which of the following statements is correct?

Statement $I$: Boron does not exhibit allotropy.
Statement $II$: Boron is an extremely hard and black-coloured solid.

Which of the following statements is incorrect?

Which of the following oxides is amphoteric in nature?