For editing Pokémon Generation 3 save files (Ruby, Sapphire, Emerald, FireRed, LeafGreen) directly on Android, you have a few reliable paths ranging from dedicated mobile apps to browser-based tools. Recommended Save Editors for Android
PKHeX (Android Port/MAUI): An experimental Android version of the industry-standard PKHeX. While powerful for editing species, moves, and stats, some users find it janky or prone to crashes on certain devices.
While not an official release, various mobile ports and "PKHeX Maui" APKs circulate in community forums like Project Pokémon
A Pokémon Gen 3 save editor is a software tool that allows users to modify their save files for Pokémon Ruby, Sapphire, and Emerald games. This tool enables players to change various aspects of their game, such as Pokémon stats, items, and even the game's storyline. With a save editor, players can experiment with different scenarios, create custom Pokémon teams, and explore new possibilities within the game.
.sav or .sgm file (in-game save, not save state)