Desert Talon
Email: erdem.durak@gmail.com
Please say which device and which iOS version you are on — it is usually the first thing that narrows a problem down.
Open the game, tap any locked mission, and choose Restore a purchase. Purchases are tied to the Apple Account that bought them, so make sure the device is signed in to the same one.
The same Restore a purchase button brings it back. There is no account to recover and nothing to transfer — Apple holds the receipt.
No. The game plays offline, and it remembers what you own without asking anybody. A connection is needed only for the purchase itself and for the restore.
Campaign progress, the aircraft you have chosen, liveries and options are kept on the device. Deleting the app deletes them; the purchase survives and is restored with the button above.
If the game stops on the loading screen, force-quit it and open it again — the top of the menu will show the step it stopped on. A photograph of that line is the single most useful thing you can send.