You connect a game link cable (avalible at most video game stores) to both of the Game Boys then go to the Trade Center on the top floor of the Pokemon Center.
You need a Game Boy color link cable.
If you can trade Pokemon from crystal version to gold version my guess is yes
Yes
There is no NPC who you can trade a Haunter to for a Gengar in Pokemon Crystal. To get Gengar you will need to trade with another player or a copy of Pokemon Gold, Silver or Crystal.
Trade it from Crystal gold or silver
trade it from silver, gold :(
Ask someone with a copy of Red/Blue/Yellow/Gold/Silver/Crystal to trade with you. Have them trade any Pokemon with you, and then trade the now-evolved Machamp back to you.
Yes
You can trade with Pokémon Red, Blue, Yellow, Gold, Silver and Crystal.
It will let you trade between Pokemon Gold and Crystal. You just have to make sure you are using two gameboy colours and a gameboy colour link cable.
no
cbcvvvYOU ARE WRONG
You'll have to trade him over from Red or from Gold, Silver, or Crystal.