Question

in an episode in sinnoh this gus raichu knows hyperbeam

Answer 1

No, if a Pokemon is to learn a move without normal circumstances its a move tutor that teaches them it, in the case of Ash's Pikachu learning Iron Tail and his Tirtwig learning Energy Ball.

Source-My watching the anime since I was little

Comments

But how did Sugar (Abigail's Raichu) learn Focus Punch and evolve out in the middle of the forest? (This is from Sinnoh) The only way I can think of is Sugar finding a TM and a Thunderstone that was dropped somewhere.