Eevee needs to happy and it needs to be night time.

You need to bred Manaphy with a ditto.

Arceus is an event only pokemon.

No, as far as the game knows they aren't real.  Zorua and Zoroark are in GV, it would be like having a Dialga in Ruby.

It there anything you can do to help its legs? Have you brought it to a vet?