If you have 2 gameboy colors, advances, or pockets and a link cable for gameboy color or pocket.
you can link soul silver with gold i dont think yellow though
yeah but you need a kind of connection cable and i doubt they still sell it anywhere
crystal,yellow,red and blue
I don't think so, because Yellow is first generation, and Gold is 2nd. They can link together, but in a limited access as Yellow doesn't have all the Pokemon in Gold. You might have more functionality if you completed the game or catched all the Pokemon in your pokedex, but I'm not 100% sure.
with a link cable
yes you can transfer a egg by link cable in the versions gold/silver/crystal. but u cant trade eggs to red/blue/yellow/green.
One can trade in Pokemon Yellow via link cable. Two Gameboy consoles can be connected via link cable and Pokemon can be traded across Pokemon Blue, Red, or Yellow.
you have to get a life!!
You cannot get an umbreon on Pokemon Yellow as they were only introduced in Pokemon Silver and Gold and from then on. You can only get Vaporeon, Jolteon, and Flareon on Yellow.
I say gold
No.
The Yellow Forest route on the Pokewalker? Pikachu. Only Pikachu.
Pikachu
Yes it can. Using the Time Capsule in Gold and Silver it's possible to trade between Red, Blue, and Yellow.