Which of the following carbocations is the most stable?

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

Which of the following molecules/species is the most stable?

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

Arrange the following carbanions in the decreasing order of stability:
$I. \ p-Br-C_6H_4-CH_2^-$
$II. \ C_6H_5-CH_2^-$
$III. \ p-CH_3O-C_6H_4-CH_2^-$
$IV. \ p-CHO-C_6H_4-CH_2^-$
$V. \ p-CH_3-C_6H_4-CH_2^-$
Choose the correct answer from the options given below:

List the reactive intermediates produced by the fission of a covalent bond and describe their main characteristics.