Retrieve data from individual app after iOS 7 update?

Question

This what I did:

1. Installed various apps onto my iPad (before the iOS 7 update was released) using another Apple ID.
2. Used the apps, so they had data in them that I would really like back.
3. Backed up my iPad 4 (still on iOS 6) onto both iCloud and my computer. (Those backups have now disappeared).
4. Installed both the latest version of iTunes and iOS 7.
5. Found that the apps were greyed out and needed the password for the old Apple ID.
6. Couldn't remember the Apple ID password (or the Apple ID) that was used to install those apps, and I only really need one, so I entered billing info, changed my mind at the last moment and set card type to none.
7. All of the greyed out apps disappeared. I changed my mind again, and bought and installed the app, hoping that I'd be able to restore it from the backup.
8. Tried to restore it, but the message said the backup was corrupt or incompatible.

I don't want to delete the backup, because it has my data on it. Is there any way to get the data back? For example, extracting an individual app's data from the corrupt backup, or could there possibly be some secret stash of backups that that I don't know about?

Answer 1

You will need to use the original Apple ID with which the apps were purchased. Only then restore from the backup made (preferably the backup made via iTunes). This is the only way to retrieve the app data associated with the given application.