Which of the following does not obey the octet rule?

What is the number of sigma bonds in $P_4O_{10}$?

The correct statements from the following are:
$a$) The total number of sigma bonds present in benzene is $12$
$b$) $LiF$ is more covalent than $KF$
$c$) $SnCl_2$ is more covalent than $SnCl_4$

$BF_3$ is used as a catalyst in many industrial processes because of its:

In the Lewis dot structure of carbonate ion shown,the formal charges on the oxygen atoms $1, 2,$ and $3$ are respectively:

Arrange the bonds in order of increasing ionic character in the molecules: $LiF$,$K_2O$,$N_2$,$SO_2$,and $ClF_3$.