1 - Download the game save backup at Download files and extract it.
2 - Delete and reinstall the app.
3 - Logout of Game Center, Open the app till you get to the menu, then close the app from the multitask.
4 - Put the documents folder in the 「Subway Surfers/Documents」 using (iFile, DiskAid, iFunBox...) or other apps.
5 - It will ask you to replace the old documents folder, do so.
6 - Launch the game and don't load save from iCloud.