Its label will give you the ultimate height and spread, if its label was lost Google the plant and you'll get its specific details come up from numerous sources and you can get your specific info better.

It depends if it is grafted onto a rootstock. The rootstock will ultimately govern the size of the plant. It will certainly get larger than it was in the pot as it will have lots more root room and moisture. Be sure to keep it well watered for the first year.

If it was sold as a dwarf tree, then it should be on a dwarfing rootstock - nonetheless, your tree will get larger, as Volunteer says. A non dwarf cherry tree can reach 40/50 feet or more, so 'dwarf' is a relative term. Last one I saw, been in the garden 15 years, was by then about 10 feet high.