Apple released the eleventh developer beta for iOS 12 to registered software testers on Monday, Aug. 27, only four days after the company unexpectedly released both dev beta 10 and public beta 8. 

As always, please back up your device before any change.

Operations

Step 1 Connect your device to PC with USB cable and launch 3uTools. 

Step 2 Head to Flash & JB → Easy Flash,  select the iOS 12.0beta11 firmware. If you want to save data, please click the checkbox “Retain User’s Data While Flashing”. Click “Flash” to start downloading iOS 12 beta 11 firmware.

Step 3 Please do not disconnect your iDevice and wait patiently until the process is finished, it would probably take 5 to 10 minutes. And after that, your device will be restored to iOS 12 beta 11. 

 If you meet any flashing error, you could view tutorial Roundup: Error Codes in iTunes/3uTools for reference. In exceptional cases, you could contact 3u Team for further support.