How did Apple 5s restore the mobile phone system from 8.2 to 7.0? After the update, the phone of the mobile phone card cannot be answered, and the flash back is serious.

1. If Apple's mobile phone system wants to achieve system degradation recovery, it must be achieved within a specified time, which can be a verification period; As long as it is within this time period, even if the equipment is upgraded, it can be downgraded and the version can be downgraded. Once this port is closed, you cannot revert to an earlier version of the system.

2. For example, shortly after the ios8 system came out, the mobile phone was updated to the latest ios8 system. Before the system more advanced than ios8 comes out, we can test whether it can be downgraded to ios7. 1.2 after sale. Or you can make a backup before the system upgrade and then try to restore it, but it is not recommended to do it yourself, which is risky.

3. As the system belongs to the software part, there may be a charge for finding the after-sale degraded system, so please pay attention here.

4. Again, it is recommended not to blindly pursue the advanced version. The more advanced the system version, the higher the requirements for mobile phone hardware. Mobile phone hardware can't meet the requirements, and there will be pressure when running, and the speed can't keep up, which will cause the mobile phone to get stuck; If the mobile phone is not delayed, but the running speed is acceptable, it is best not to upgrade the system.