Can a Pokemon re-learn a "transfer-only" move?

Question

I'll use an example: I had an Entei from an event in a gen 4 game that knew Crush-claw and Extremespeed but had made him forget in favor of a different moveset. If I transfer this Entei to my copy of ultra sun, is it possible for the move relearner to teach him those moves since he knew them at one time or not because they aren't moves entei normally learns?

Comments

Nice solution

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I'm pretty sure Generation 4 games don't really record moves that Pokemon forget, and the move reminder only looks at the Pokemon's level up learnset. I'm much less sure about what happens when a Pokemon first transfers to Generation 7 and then forgets the move.

Answer 1

From Generation VI onward, any Pokémon hatched in Generation VI onward may also be taught any move it knew when it hatched; this includes Egg Moves, Volt Tackle bred onto Pichu, as well as any level-up moves the hatched Pokémon knows upon hatching. Also in these games, Pokémon obtained via Mystery Gift can learn any specifically flagged move it knew when it was obtained; early Generation VI distributions only flag event-exclusive moves (such as the Pokémon Center Tokyo Bay Inkay's Happy Hour) and Egg Moves, whereas later Generation VI distributions and all Generation VII distributions flag all moves the Pokémon knows when obtained except moves introduced part-way through that generation.

source
I think it's safe to assume that events in earlier generations didn't flag any of their moves, so forgetting the moves means forgetting them forever.