Titanium Backup Pro is a very effective backup and restore tool. It also has several other functions for your apps.
Functions:
Makes several backups for each app without the need to close them, and restores SMSs, MMSs, calls, bookmarks, Wi-Fi and AP as well as XML.
Activities:
Restores individual apps and CWM, TWRP and ADB data backup without root. Can also freeze applications and perform encryption.
Recommendations:
If you can not download your PRO key, try the web version of the Play Store. If the problem persists, go to checkout.google.com to cancel your order and try again.