Alolan Raichu cannot be achieved by breeding in any region besides Alola because the bred Pokémon, Pichu or Pikachu, aren’t Alolan forms themselves, so will evolve into the region Raichu form. The Everstone will not affect this.
Normally, when breeding a Pokemon with alternate forms, the offspring will hatch as the form native to the region you're in--so Vulpix will always be normal, because that's the kind of Vulpix you can get in Galar. Once you transfer in an Alolan Vulpix, though, you can breed more Alolan Vulpix by giving it an Everstone to hold before putting it in the Nursery. This will pass down the parent's form to the offspring, but it only works if the parent is female or if you're breeding with Ditto. This also only applies if the Pokemon that will hatch also has an alternate form; for example, breeding an Alolan Raichu that's holding an Everstone won't get you an Alolan Pikachu because there isn't such a thing. It will instead be a regular Pikachu, and in Galar[or any region besides Alola], Pikachu will always evolve into regular Raichu.
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