Can Gen 1 TMs be traded between RBY and GSC?

Question

Can a Gen 1 Pokemon from GSC be traded back to RBY with a Gen 1 move that it can't learn in RBY? For example: A Machamp that learns Fire Punch in GSC being traded back where there is no way it can learn the same TM in RBY.

Comments

If a move on a Pokémon is not registered in the Gen 1 code, it will be recognized as a glitch Pokémon or hacked Pokémon. Simple as that.

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if the game does not recognize a valid pokemon, it is taken as a glitched/hacked poke. so if you use fire punch on that machamp, it is a glitched / hacked pokemon in gen 1

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I’m about 90% sure that, as long as both the Pokémon and the move exist in Gen 1, it’s possible to transfer that Pokémon without getting a glitch, even if it’s only possible for the Pokémon to learn that move in Gen 2.

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Recommended reading for anyone who can transfer between the first 2 generations: https://www.smogon.com/articles/rby-tradebacks-ou

Answer 1

Your Machamp would most likely be able to be transferred back to your copy of RBY without any issues, provided it doesn't know any moves that don't exist in Gen 1. Fire Punch is a special case because it exists in RBY, while other moves like DynamicPunch would make your Machamp glitchy. If you're looking to transfer it backwards, make sure it knows no moves that are only available from Gen 2 onwards, otherwise it could be very dangerous to your game.