Umbreon
Eevee's Dark-type evolution form is named Umbreon. In the primary core games, Eevee evolves into Umbreon when it has full Happiness during the night.
In FireRed and LeafGreen, the pokemon that evolve via the firestone are as follows: Eevee (into Flareon) Growlith (into Arcanine) Vulpix (into Ninetails)
The Pokemon is JOLTEON you can get one by using a thunder stone on an EEVEE you can get an EEVEE by going in the house next to the Pokemon centre in hearthome city, -i think- but just check every city and the houses next to the Pokemon centre's, hope this helps!
Houndoom
Yes, find a trader who will trade you a ditto. Then put in daycare and a few days later.... WALLA you have three or four eevee eggs. Sources Happened to my friend he gave lots of eevee. His name was fregley. LOL. :)
go to hearthrome and go to the right of the Pokemon center and her name is bebe and keep talking to her and she will give you a evee
in hearthome city next to the Pokemon center
Darkrai
Shinx-luxio-to luxray Dialga,Staraptor,eevee,Jolteon,Darkrai i name all there`s more than 300 Pokemon! get the Pokemon diamound book you can find it at BlockBuster
Go to http://pokemon.marriland.com/diamond_pearl/pokedex/list/all/ it will show you all of the pokemom. It even show you there picture there name there type and even there Original stat. By cliking on the pokemons name, it will show you the picture of that pokemon. If you scroll down you will is an Evolution line of the pokemon. this website rock
I'm not sure but maybe it could be Daria the dark ghost Pokemon or the Pokemon who can change in other Pokemon (Pokemon movie 13) I can`t say the name because the movie 13 starts in June 6 (not sure)
Yes, they will alert you and say, "There seems to be an interesting Pokémon in [Kingdom's Name]!" You can link with it.