Which of the following has an unstable enol form?

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

The correct order of increasing stabilities of the following carbocations is:
$(i)$ Allyl carbocation
$(ii)$ Ethyl carbocation
$(iii)$ Benzyl carbocation
$(iv)$ Isobutyl carbocation

In a carbonium ion,the carbon atom bearing the positive charge is in the:

The most stable carbocation is

State True or False for the following statements:
$(i)$ Only carbocation is formed by homolytic cleavage of a bond.
$(ii)$ By heterolytic cleavage of a bond,a carbocation or carbanion is formed.
$(iii)$ The carbon of a carbanion is $sp^2$ and the carbon of a carbocation is $sp^3$.
$(iv)$ The carbon of a carbanion is $sp^3$ and the carbon of a carbocation is $sp^2$.