Spells that summon from another dimension would not be allowed at this time, no. If a creature is brought with the character as a pet or familiar and the spell summons that creature, then that would be fine as long as it is limited in some way.

This would depend on the size of the mount. As long as the mount is no bigger than the size of your average motorcycle, they are a-okay! If you would like them to be brought in anyway, then they will be shrunk down to the general size of a motorcycle upon entry as that is the size of the animal housing that the cities maintain.