The 1635 - Pokémon Fire Red (U)(Squirrels) ROM is widely considered the gold standard for the GBA hacking community. While it is essentially a "clean" dump of the original Pokémon FireRed Version 1.0 (US)
Gameplay Changes
Disclaimer: This report is for informational purposes regarding the identity and features of a software modification. Distributing or downloading copyrighted ROM files is illegal in many jurisdictions. Always support official releases by Nintendo and The Pokémon Company. 1635 pokemon fire red usquirrelsgba rom exclusive
An exclusive ROM hack means:
What's the difference between different roms? : r/PokemonROMhacks The 1635 - Pokémon Fire Red (U)(Squirrels) ROM