What is the correct formula of Borazole?

$B_4C$ (boron carbide) is used except:

Which of the following orders is not correct against the given property?

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 of the following oxides is amphoteric in nature?

Give important trends and anomalous properties of boron.