iMac having graphical issues and some apps simply get stuck.

Video showing the Graphical issues.

MacOS 15.5 on iMac 2013 27 inch.

One thing I did find is that , whilst attempting to reinstall post install root patches , it complained of a mismatch

SystemVersion.plist build version mismatch: found 15.6 (24G84), expected 15.5 (24F74) An update is in progress on your machine and patching cannot continue until it is cancelled or finished

And doing a check in System Settings , iMac unfortunately downloaded 15.6.

1. Is there anyway to fix this graphical issue , without reinstalling post install root patches

2. If no, is it safe to update the macOS via system settings and then reapplying post root install patches after that’s done?

3. Any other fixes you guys can recommend?