Normally Apple will give users a period of time to be able to undo a lower version of iOS after they release a new update .And when Apple locked the sign of an iOS version, we couldn’t go back to that version anymore, if we tried to download the firmware to restore it would be a bug 3194 .
So in this article I will share with you the site is just a source of downloading iOS firmware, both a place where you can check which version of iOS is still available to restore, and which versions have sign lock.
You go to the website https://ipsw.me/, then select the correct iOS device you are trying to check or want to download the firmware for it.
Immediately after that, select the firmware to download. Firmware with licensed restore is in the Singed IPSWs section with the green mark, the locked firmware is below with the red mark. You can still download the locked firmware but will not be able to restore it because of a 3194 error as mentioned above.
For example, for iPhone 7 Plus, we can now restore the following versions: iOS 10.2 (14C92), iOS 10.1.1 (14B150), iOS 10.1.1 (14B100) and iOS 10.1 (14B72c)
Outside We can also check which iOS versions can be jailbroken, as well as the appropriate tools to jailbreak them. Click on the line “You can’t jailbreak iOS 9.3.4 -> 10.2” to see it.
Many of you know iOS as well as many other sites with similar check. However, I see that many members still ask this issue, so I do my homework to make it clear.