My safari stopped working and froze. I rebooted and tried to open a shift key down, but safari flickers but will not open and I get a report window. Last night it occurred and I reloaded the most recent update (which I had done hours earlier)

afe Boot, (holding Shift key down at startup), does the problem occur in Safe Mode? Could take 10 minutes.

Safe mode attempts to repair Disks & clears lots of caches & loads safe Drivers, & prevents loading of 3rd party extensions, so if Safe Mode works try again in regular boot.

If that doesn't cure it...

Start up from macOS Recovery

To start up from macOS Recovery, turn on your Mac and immediately press and hold ...

Command (⌘)-R

Installs the latest macOS that was installed on your Mac.

There have recently been many reports of a broad range of new problems on this support site about the latest release of Safari v15. It is included in the downloads for Big Sur and Catalina. If you are experiencing these problems, you can use another browser such as Firefox or Chrome and they will work for you until a newer version of Safari is released.

I have read here that Apple's support people have a link to reinstall Safari and that doing so often fixes the problem. You might check with them.