I cannot restore my backup on iOS9 beta 2, it fails with generic error after 10 minutes.
Scenario:
1. iOS9 beta 2 - iTunes 12.2.0.145 on Mac Yosemite
2. Backup with password [OK]
3. Reset iPhone [OK]
4. Restore previuos backup with iTunes [FAILS with generic error text, no error code]
I tried to restore the same backup from another pc (Windows), and the result is the same.
I think it depends on iOS9 beta2.