There is one in Vermillion City. You need a Spearow to trade for a Farfetch. Look in one of the houses, you will find a little girl. She trades.
There is also a little girl in the underground Path that stretches from the route 5 to route 6. She will be next to the stairs in Route 5 part of the underground path. She will trade you male Nidoran if you give her a female Nidoran.
At the Elite Four or battle NPCs with Pokemon the same level as your one.
you can't
In Pokémon LeafGreen, you can trade Pikachu to other players or NPCs who are looking for it. One notable NPC is in Celadon City, where you can trade a Pikachu for a Machoke. Additionally, you can trade with friends who are playing Pokémon FireRed or other compatible games to complete your Pokédex. Just ensure that you have a Link Cable or use the wireless trading feature if available.
No, you need to TRADE from RSE.
You don't. Girafarig can only be obtained in Pokémon FireRed or LeafGreen by trading it in from another game. Or you can use this GameShark code: 17543C48 E65E0B97 41377A90 E36247DE
Erik and Sara are NPCs in Pokémon FireRed and LeafGreen. It is not possible to get them back together in the game.
At the Elite Four or battle NPCs with Pokemon the same level as your one.
You can get an Electabuzz in LeafGreen by TRADING it form Firered.
By trading it from FireRed or LeafGreen.
you can't
In Pokémon LeafGreen, you can trade Pikachu to other players or NPCs who are looking for it. One notable NPC is in Celadon City, where you can trade a Pikachu for a Machoke. Additionally, you can trade with friends who are playing Pokémon FireRed or other compatible games to complete your Pokédex. Just ensure that you have a Link Cable or use the wireless trading feature if available.
With another person yes, and at the trading post es, but with NPCs? no.
You can't
you cannot catch celebi in Pokemon leafgreen. you can only get it through cheat codes or trading.
Only by trading from LeafGreen and/or FireRed
Only by trading it from Leafgreen/Firered.
It is not possible to get all three starters in Pokemon LeafGreen without trading. This was an intended mechanic to encourage interaction between players.