What people did not think is that Apple actually secretly opened the downgrade channel, if you are not satisfied with the current iOS version, you can completely return the original version.
After the actual query you can clearly see, iPhone 5, 5S, 6, 6S, 7 series models of the old firmware, Apple has opened by default downgrade channel, so if you are willing to return to the original system, bid farewell to the restrictions The dilemma of performance:
1, iPhone 5 can be reduced to iOS 6.1.3;
2, iPhone 5S can be reduced to iOS 7.0.3;
3, iPhone 6, 6S, 7 can be reduced to iOS 10.2;
There are currently users have measured the success, it is indeed possible to downgrade, such as iPhone 5S successfully downgrade iOS 8.0 system, but now the server is a bit busy, we may wish to try later, as to when the closure is not clear.
Of course, if you want to go back to the old version, the method is as simple as:
1, connect the device with the latest version of iTunes with data cable, then open iTunes,
2, hold down the keyboard Shift, at the same time, click iTunes "update" function;
3, according to iTunes pop-up dialog box, select the appropriate version of the iOS firmware (provided that you need the firmware under the good), click update.
In particular, to remind that before Apple announced in the official announcement, iPhone 6,6 Plus, 6S, 6S Plus, SE models are limited performance since iOS 10.2.1, while iPhone 7,7 Plus is from iOS 11.2 Began to be limited performance.