Homolytic fission of $C-C$ bond in ethane gives an intermediate in which carbon is

Stability order of the following carbocations is:
$(i)$ $CH_3-C^{+}(CH_3)-CH_2-CH_3$
$(ii)$ $CH_3-CH^{+}-CH_3$
$(iii)$ $CH_3-C^{+}(CH_3)-CH_3$
$(iv)$ $Ph-CH^{+}-CH_3$

$:CCl_2$ is

The most stable carbocation among the following is:

The compound shown below undergoes racemization on reaction with aqueous acid. Which of the following structures best represents the intermediate responsible for this process?

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