1. Flareon - Fire Stone
Vaporeon - Water Stone
Jolteon - Thunder Stone
Espeon - Happiness Day
Umbreon - Happiness Night
Leafeon - Level Up Eterna Forest
Glaceon - Level Up Route 217
2. Apart from "Bug", they cover each others weakness (psychic beats fighting beats dark beats ghost beats psychic)
Helping Hand + Power Swap. If used repeatedly, attack stats can be boosted to the max.
3.Eevee - Dark Grey (G2) White (G3, G4)
Flareon - Orange (G2) Gold (G3) Brown (G4)
Vaporeon - Purple
Jolteon - Darker yellow (G2) Green (G3, G4)
Espeon - Green
Umbreon - Purple/Blue (G2) Teal/Aqua (G3, G4)
Leafeon - Slightly more saturated (hard to notice)
Glaceon - White
4. Espeon - Morning Sun
Umbreon - Moonlight
5. Your question is wrong, but whatever.
Found in Celadon Mansion in Red, Blue, Yellow, Firered, Leafgreen
Gifted by Bill in Gold, Silver, Crystal, Heartgold, Soulsilver
Gifted by Bebe in Diamond, Pearl, Platinum
Starter Pokemon in
Not available in Ruby, Sapphire, Emerald, Coliseum
Also available for purchase in the Game Corner for 6666 coins in Gold, Silver
6.