All of the smartphones don’t support rolling back the system version. Rolling back the system version, or downgrading the operating system (OS) on a smartphone, can have several disadvantages.
For your reference, here are the key points to consider:
1. Older OS versions may have security vulnerabilities that have been patched in later updates. Downgrading could expose your device to these risks;
2. Older OS versions might have unresolved bugs and glitches that were fixed in subsequent updates;
3. Manufacturers and app developers focus their support on the latest OS versions. Rolling back means reduced or no support for troubleshooting and technical issues;
4. The process of downgrading the OS can sometimes go wrong, especially if not done correctly. This can result in the device being "bricked," or rendered unusable.