Every mon up to Gen 5 (#1-#649) is in the game and obtainable by the player, of which ~500 can be obtained through what I'd say are "regular" means, including all non-starter non-legendary Pokémon. I don't plan to introduce Gen 6+ for practical (it would take massive effort) and balance reasons...
There is a Battle Tower, a Battle Factory, a Battle Palace, and a Battle Arena. There are 2343 different Pokémon sets, of which 1328 are used for the Battle Tower, Battle Palace and Battle Arena, which have no progression per se and essentially start already at maximum difficulty. The remaining...