Simply launch 2Do, tap on Sync->Backup->Auto Backups and tap on a backup (it will list the last 30 automatically created backups) to restore immediately. Restoring the db will allow you to sync again or simply change/alter your data from a previously taken snapshot.

Users who do NOT use sync: Auto backups are still very useful. Every day 2Do will automatically create a backup for you. If you think you lost some tasks or would like to go back to a previous backup, simply navigate to the ’Auto Backups’ screen and tap on a particular backup to restore.