Send me to hell if I´m wrong, but I believe you have to get the national pokedex.
How to get the national pokedex? SEE all the pokemons!
Crystal most likely because that's how it is in the manga
go to prof. elm and he'll give you a starter Pokemon from y/r/b
after you beat red[in mt silver] , go to prof oak and he will give you a Pokemon
After defeating Team Rocket, you need to go to Prof. Elm. He will give you a Masterball if you talk to him.
After you have defeated all 8 gym leaders, go to prof. elm. He will give you the masterball.
Prof. Rowan does as your starter . U can choose piplup, turtwig, or chimchar
No, Bill does, and you can buy them from Cerulean City Game Corner for 9,999 Game Corner Coins
Go back to pallet town and visit prof. Oak. He will give you access to Mt. Silver in Johto which houses the strongest trainer in all current Pokemon games. You can challenge Red at the top of Mt. Silver but be warned his Pokemon are level 80 and up. If you beat Red then prof. Oak will give you a Kanto starter Pokemon and Steven (in Saffron City's Silph Co building) will give you a Hoen starter Pokemon.
you have to pick between a.bulbasor b.squirtle c.charmander
"you have to beat all 8 gyms then go to pallet town,go to the prof. and he well let you get one." This is incorrect. Proffessor Oak will give you a KANTO starter. For a Hoenn starter you have to meet Steven Stone in Vermillion City which will allow you to track Latios/Latias. THen you have to have all 16 Gym badges AND beat Red and you will be able to get a Hoenn Starter in the Silph Co.'s building from him. You can also get a Kanto Starter from Prof. Oak at this point.
This is only in silver, gold, crystal and heartgold and soulsilver but you need the get the first badge then prof elm will call you mentioning his aid is in the Pokemon center talk to him to receive the egg.
you fill the whole sinnoh pokedex and then go to prof rowan and prof oak comes in talks and then you help him out easy as that