I've decided to make this video because there were a lot of methods to save SHSH2 blobs lately and some of them unfortunately are not compatible with Prometheus (FutureRestore) Downgrade so they can't be used to go back from iOS 10.2.1 to iOS 10.2. Ever @tihmstar has created prometheus downgrade tool, a lot of SHSH2 tickets saving tools were created: TicketBox, TSS Saver, a SHSH2 Bot for Telegram, TSSChecker, etc. Unfortunately, some of the blobs were saved in a wrong format: i.e. Missing ROSI Tag, missing generator, bad format, incomplete digests, etc. So in this video I will show you how to verify the blobs you have saved to ensure you can use them to downgrade in the future. Some of the blobs were saved correctly but because people used a bad boardconfig, they won't work with their specific device, in the video I show how to check that as well.
You should repeat this procedure every time you save your blobs for a version, and yes, you should save your iOS SHSH2 blobs for any version that appears, you never know when you need to go back to a specific firmware like iOS 10.2.1 or iOS 10.3 Beta.
I have plenty of tutorials on saving SHSH2 correctly, I will attach some down here.
TSS Saver (and checker): //tsssaver.1conan.com/check.php
How to save iOS 10.2.1 Blobs: //youtu.be/Mzxpt_o578s
Downgrade from iOS 10.3 Beta to iOS 10.2: //youtu.be/WXs-dpwLhkc
Untethered iOS 9.3.5 Jailbreak: //youtu.be/3lGMppIcOyU