the decision is final
Yes
No
they evolve from ponies ( the same one on the cartoon I hear) get high high enough and they even touch you
Vouchers
the decision is final
Just go to Ponyville, you'll find plenty
Yes unicorn ponies are real.
More information on the topic.
Now, as for real physical unicorn horses, no they are not real.
Id hate to break it to you, but no they don't exist.