iMac Monterey Updates
Running Monterey 12.6.3. Is there an update? Don't see one in System Preferences.
Monterey 12.6.3 was the last version of Monterey before Ventura. So if an upgrade to Ventura isn´t showing in System Preferences this probably means your Mac can´t run Ventura. Here´s a link to Apple shwing all Macs which are compatible with Ventura:
macOS Ventura is compatible with these computers - Apple Support
If your Mac is shown as compatible then boot into Safe Mode: Start up your Mac in safe mode – Apple Support (UK) Safe Mode often cures glitches and other problems.
Then re-boot normally and see what System Preferences says. Cheers, Ian.