Which of the following carbocations is most stable?

Explain why $((CH_3)_3C)^+$ is more stable than $(CH_3CH_2)^+$ and $(CH_3)^+$ is the least stable carbocation.

Which of the following is not expected to be an intermediate of the following reaction?

Among the given compounds $I, II, III$,the correct order of bond dissociation energy of the $C-H$ bond marked with $*$ is:

Identify the correct order of stability for carbocations.

Arrange the following carbanions in the order of their stability:
$i$. $RC \equiv C^{\ominus}$
$ii$. $C_6H_5^{\ominus}$
$iii$. $R_2C = CH^{\ominus}$
$iv$. $R_3C - CH_2^{\ominus}$