https://support.apple.com/en-us/HT201222 - Apple 

https://lists.apple.com/mailman/listinfo/security-announce  - Sign up for Apple email announcements (offers more details)

Officially the only version of macOS that Apple will patch all published security issues will be the latest patch of the current O/S. So, today, that would be macOS 13.3 Ventura. 

Apple may release patches for older versions of Big Sur and Monterey, not all security flaws may be patched. There are some security flaws that are still in Big Sur and Monterey that have been patched in Ventura for several versions. 

That being said, if you are using the latest patched version of any of the support O/S versions (Big Sur, Monterey, and Ventura) you are pretty safe. 

Thanks for your response. 
Just facing lots of update issues while updating the macOS using the below.

- Remote Command (Sometimes it works and sometimes not.)

- Lots of things to tackle as we have Intel-based mac devices and M1 and M2 as well. I wish devices can be upgraded easily.