Download the following complete development system package, put it in the storage of the mobile phone after downloading, remember the location, then open the system update of the mobile phone, click the menu button above, choose to manually install the system package, then find the system package you downloaded, install it, the mobile phone will restart, wait patiently, and enter the latest development system after installation. Remember to back up the mobile phone data to the computer, not to the built-in storage of the mobile phone, because the stable version will erase all the data of the mobile phone.