iOS 11.3, the latest version of Apple's iPhone and iPad operating system, is coming this spring, here what's new features -- and here is first beta in 3uTools. You could upgrade your device without losing data.
Step 1 Connect your iDeivce to PC with authentic USB cable and then launch 3uTools.
Step 2 On Flash & JB part of 3uTools, click Easy Flash and then select iOS 11.3 beta firmware. Click on option "Retain Users' Data While Flashing" if you want to save data.
Step 3 Do not disconnect your iDevice until the update has finished. It can take a few minutes.
Your device will be updated to iOS 11.3 beta and reboot once or twice automatically during the process.