(a) In self pollination, pollens from the anther are transferred to the stigma of the same flower or another flower of the same plant.
In cross pollination, pollens from the anther of one flower are transferred to the stigma of the another flower of another plant but of the same species.
(b) When an insect sits on a flower, the pollens from the anther stick to their wings. The same insect when sits on another flower, the pollens from its wings stick to the stigma of that flower thereby affecting pollination.
(c) Pollination is the transfer of male gametes onto the female gametes, while fertilisation is the fusion of these two gametes.