1) Cotyledons or seed leaves are the first leaves formed by the seedling. It starts photosynthesis and seedling grows. Without turning green, no photosynthesis will occur and the seedling will die.
2) On the basis of seed leaves or cotyledons plant are classified into monocotyledons - one cotyledon and dicotyledons - two cotyledons .
3) They are called as Gymnosperms.
4) Yes, we can identify them monocotyledons have isobilateral leaves with parallel venation and dicotyledons have dorsiventral leaves and reticulate venation.
5) If pollination does not occur, there will be no fertilization and consequently there will be no seed formation. The flower will just wither away. It will not change into fruit.