: You must provide your own Sonic 3 & Knuckles ROM file (typically named Sonic_Knuckles_wSonic3.bin ). The app will ask you to select this file the first time you open it.
ROM hack exactly as it appears on PC, you can use a Genesis emulator. How can I play sonic 3 on mobile? : r/SonicTheHedgehog sonic 3 complete download portable apk android
Save files disappear after closing the app. Solution: Grant the APK "Storage Permission" manually in your Android settings. The app needs permission to write a .srm save file. : You must provide your own Sonic 3