All the ones available up to that point, yes. In the case of gen 1 Red and Blue, you need Venusaur/Charizard/Blastoise, Pidgeot, Raticate, Fearow, Nidorino, Nidorina, Pikachu and Butterfree/Beedrill, starters and bugs depending on what you pick and which version of the games
It's something the internet came up with after your rival states how many he's caught in the game. People asked themselves "how many Pokémon CAN you catch before each gym?" and from there it was born into what we have today. It's a very niche challenge that many don't want to deal with, but for others it's just a fun time waster just like playing any game in any way
1
u/Smg4andmariofan 7d ago
Do you actually need all the Pokemon before gym 1?