Apple’s walled garden is simpler but stricter. Your save is tied directly to your Game Center account.
Let’s address the elephant in the dungeon. Unlike many modern mobile games that automatically sync to Google Play or Game Center, Grim Soul has a complicated relationship with cloud saves. grim soul save data
The Golden Rule of Grim Soul: Never trust cloud saves alone. Always maintain a manual local backup. Apple’s walled garden is simpler but stricter
Want to move from an old phone to a new one? Here is the survival guide. The Golden Rule of Grim Soul: Never trust cloud saves alone
Android → Android: Easy. Copy the UserData folder from the old phone to the new phone using the restore method above. It works seamlessly, even across different Android brands (Samsung to Pixel, etc.).
iOS → iOS: Use the iTunes encrypted backup method or the direct "Quick Start" wireless transfer during iPhone setup. This moves the save data along with everything else.
Android → iOS (or iOS → Android): You cannot. This is the brutal truth of Grim Soul. The save file format is platform-specific. The Android hero.dat file is not compatible with the iOS sandbox. If you switch ecosystems, you are starting over. There is no official cross-platform save transfer, nor a "code" system.