>>725312749
Short answer: Not every Pokemon in every game, but if a Pokemon is in a new games Pokedex, you can transfer from older games to the newer game, and in some cases, even send them backwards.

Long answer: All Pokemon, with the exception of some extreme fringe cases, can be transferred to Home. Home is a subscription service that allows you to store your Pokemon (though I think you can get 30 spaces for free, subscription just gives you access to thousands of space for convenience).

Each Pokemon game since Sword and Shield has its own Pokedex, and only what is in that dex can be caught and transferred in and out of that game. This means some Pokemon are in some games and not others.

From Home a Pokemon can be transferred to any game they are compatible with, but which games will depend on their source game. Any Pokemon from Sword/Shield, BrilliantDiamond/ShiningPearl, Legends: Arceus and Scarlet and Violet can freely travel between those games so long as they are in that games Pokedex.

Pokemon from those games can travel to Legends Z-A when that's made compatible as well, but doing so will make them no longer able to be transferred to the older games. Similar Legends Z-A caught mons can't go back to the other games. However any Z-A mons (either old mons moved to Z-A, or new mons caught in Z-A) will be compatible with future games - again only if they are in that games pokedex.