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So we know that non-Alolan forms of Pokémon can be obtained by breeding a non-Alolan Pokémon holding an Everstone.
But how do you acquire Raichu, Exeggutor and Marowak? While Sandshrew will only evolve into Sandslash and Alolan Sandshrew will only evolve into Alolan Sandslash, these three are unique in that they evolve into non-standard forms. Is it not possible to evolve a gen 7 Pikachu into regular Raichu?