Nostalrius Begins - Quality wow vanilla realm (1.12)

Hey everyone, this is obviously old news to some but I have some questions if someone can answer them.

First
Is nostalrius coming back and will it be under Elysium? or will it just be nostalrius like before?

Also I understand that our old characters can be restored, any idea how this is done? Will there be a new client download? confused about the whole thing. Also, when does this launch?

thanks