The mobile phone MIUI system brings more playability, and the update is also very fast. After updating the database version every time, it is basically impossible to support the old database version. If you return to the old version, some programs will not start or contacts will be lost.
It is not recommended to downgrade the machine after upgrading. Forced downgrade may cause system anomalies. It is recommended that you use the newly developed/stable version of the system.