if a plant has two kinds of flowers on the same plant where will the seeds form?

Answer 1

If the plant is producing two kinds of flowers from the same stem then it is probably a product of cross pollination. Flowers are created when the pollen from one flower is introduced to another by transference. Usually done by bees and the wind. Not all plants will produce a 'seed'. Of course, the plant in question could be dormaint and will not produce anything.

Answer 2

I have seen apple trees that have 5 different kinds of apples because the limbs have been grafted onto one tree...

each branch has different flowers and each branch produces different apples.. thus different seeds.