In this hack, the starter Pokémon is invariably replaced with a level 5 with boosted stats. The ROM likely retains the Kanto region map but changes the Pokédex to feature "Rodent and Sciuridae" (Squirrel family) only.
If you are looking for this specific ROM, you are likely trying to play one of these popular enhancements: Pokémon Radical Red 1636 Pokemon Fire Red Squirrels Rom
Technical details would be important here. How do ROM hackers modify game data? They use tools like hex editors, disassemblers, and maybe custom software to change sprite data, move sets, and other game elements. I should explain that process briefly, without getting too technical for a general audience. In this hack, the starter Pokémon is invariably
