So you didn’t know about Bulbapedia, or Serebii. Fair enough. There are bunch of sites online (beyond those 2) that document details surrounding moves, what Pokémon can learn them, special moves due to certain circumstances, special abilities, where to catch mons, etc. They’re all not associated to the program, and the program doesn’t use those details for the determination (the devs are also mighty dataminers). Those resources would be a good place to start if you want to try to figure anything out for yourself.
As for the Kyogre question, just inject the needed legendary with the correct origin game into your box, then withdraw it into your party, then go to the particular spot/area. That should do the trick. You can just choose one from the encounter database, and make sure you change the origin game (if it isn’t correct).