You must have the original 1636 Fire Red Squirrels ROM file.
Many mods using this base feature improved AI and competitive team building for Gym Leaders. Expanded Pokedex
The term "1636" refers to the specific scene release number for the North American version of Pokémon FireRed. In the world of ROM hacking, not all versions of a game are created equal. Different regional releases or subsequent revisions can have slight variations in code. The Gold Standard for Modding 1636 Pokemon Fire Red Squirrels
For many, 1636 Pokemon Fire Red Squirrels is the gateway to "Quality of Life" (QoL) improvements that the original 2004 release lacked. By using this base, players can enjoy: Modern Mechanics
Most ROM hacks are distributed as "patches" rather than full games to avoid legal issues. These patches are designed to overwrite the code of a very specific file. If you use a version other than the 1636 Squirrels dump, the game will likely crash or experience game-breaking bugs because the "offset" (the location of the data) won't match. You must have the original 1636 Fire Red Squirrels ROM file
If you are just looking to play a standard game of Pokémon, any FireRed ROM might work. However, "1636" is the specific requirement for those using patches (.ips or .ups files). Compatibility
Load the newly patched file into an emulator like mGBA or VisualBoyAdvance-M. In the world of ROM hacking, not all
💡 Always check the "ReadMe" file of any ROM hack. It will almost always explicitly state if "1636 - Pokemon Fire Red (U) (Squirrels)" is the required base.