Which of the following carbocations is expected to be most stable?

Which of the following carbocations is the most stable?

In which pairs,the first ion is more stable than the second?

Identify the most stable free radical from the following.

Which of the following is most likely to undergo a favorable hydride shift?

Arrange the following in decreasing order of stability.
$(i)$ $CH_3^{\bullet}$,$(CH_3)_3C^{\bullet}$,$(CH_3)_2CH^{\bullet}$ and $CH_3CH_2^{\bullet}$
$(ii)$ $CH_3CH_2^{+}$,$(CH_3)_3C^{+}$,$(CH_3)_2CH^{+}$ and $CH_3^{+}$