Final iOS 11.4 is out, and it brings with it a number of new features, along with the usual bug fixes and improvements. Check news for details. Now, you could upgrade to Final iOS 11.4 on 3uTools.

Please back up your iDevice as always before you restore your device to another iOS version.

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

Step 2 After 3uTools successfully connects your iDevice, navigate to "Flash & JB" -> "Easy Flash", there are compatible iOS version options and please select iOS 11.4 firmware. (Select the checkbox "Retain User's Data While Flashing" if you want to reserve data on your device.)

After you click "Flash", there will be a popup, read it deliberately and click "OK" to start flashing.

Step 3 Please do not disconnect your iDevice until the update has finished. It can take a few minutes. Your device will be updated to iOS 11.4 and reboot once or twice during the process.