Pre loaded games in the Anbernic rg35xxsp and how to add new games

Hey guys,

I'm entirely new to this emulator scene. I wanted to buy a gameboy emulator for my brother who loved his original GBA.

I scrolled the sub and was thinking of any of these consoles - Anbernic RG35XXSP Miyo Flip V2 (Is the hinge still bad from v1 ?)

The main question was regarding OS and games. I watched a video where onion OS was installed in Miyo but can it also be installed in the Anbernic?

Finally, are the Pokemon games installed in the emulators ? I am buying them primarily for Pokemon and dragon ball (my brother loved those).

If they aren't how to install them ? Is it paid or downloadable or something?

Thanks a ton !

I know some questions are pretty dumb but would appreciate any help !!