Restore iOS 11.3.1 with SHSH BLOBS. upgrade or downgrade your iPhone firmware to iOS 11.3.1 using blobs. for this method, you have to have saved your blobs already. since iOS11.3.1 is no longer signed and Pwn20wnd release a tool that uses an exploit by Ian beer which not requires a paid developer account. It may take a lot of tries due to the nature of the underlying exploit. Keep trying it will not panic your device if your device reboots its normal.
Once you download noncereboot1131 you must copy and paste your generator or your nonce app on the device. you just click copy on your Mac and just type it in manually. it will say success the generator has been added. Once done you can just close the app now and continue on your computer again and open futurerestore make sure to already have your blob saved in the same folder. you also need iPSW that you downloaded earlier from ipsw.me.
Full video tutorial: How To Upgrade To iOS 11.1.2 With SHSH Blobs
Restore iOS 11.3.1 with SHSH BLOBS
Downgrade or Upgrade iOS using FutureRestore and SHSH blobs. In this example, in the video tutorial, you will see an upgrade from iOS 10.3 to iOS 11.1.2 using the iOS 11.2.1 baseband and SEP but this tutorial will work for most versions of iOS for iOS11.3.1.
code you need to insert on the terminal to run with futurreestore :
./futurerestore_linux -t yourshsh.shsh2 -b baseband.bbfw -p BuidManifestOTA.plist -s sepfileforyourboard.im4p -m BuidManifestOTA.plist -d ipswtodown/upgrade.ipsw
Files you need download:
Latest compiled version can be found here:
(MacOS & Linux)
If you want do downgrade iOS11.x to ios10.x you can use this BuildManifest OTA for your device