Some community-made "Lite" versions exist, but even these typically range from 200MB to 400MB at minimum because they must still include basic models and world data. A 50MB version would lack almost all textures, audio, and cutscenes, making it unplayable. Official System Requirements
I visited popular Android modding forums (including XDA Developers and Platinmods) to see if any credible modder has achieved 50MB. gta san andreas android highly compressed 50mb
Some 50MB downloads are actually just mod packs (like ENB graphics or menu updates) intended to be added to an already installed game, not the game itself. Some community-made "Lite" versions exist, but even these