Catalina 10.15.7 on imac 27"( late 2012) has been shutting down unexpectedly
Apparently this imac can not install a latter version of OS 11 or 12.
One of the recommended fixes was to reinstall operating system. Ran the 2022-005 Catalina security update. Then ran malware and quarantined 2 malware issues. Does the update reinstall a total clean copy of Catalina? Or do I need to run a reinstall under recovery mode and then run the security update a 2nd time?
iMac 27″, macOS 12.5