For many years I was tormented with the appearance of the icon in the dock as a red icon with a white outline, solved this problem by replacing the fileo and cleaning the cache finder and dock

you need to change icns file to next

/Applications/Opera.app/Contents/Resources/app.icns

After than restart finder & dock caches

touch /Applications/Opera.app
killall Finder

sudo rm -rf /Library/Caches/com.apple.iconservices.store
sudo killall Dock

Full solution with icns file post here www.clevergod.net/Opera-icns-1a45cf4c2b3e80c6b4accdcc00286b8b?pvs=74

All tabs of Opera One(v. 100.0.4815.54) (macOS ARM & windows 11) including pinned tabs are closed
Browser crashes often, after rebooting laptop and PC all fixed tabs are closed, it is impossible to restore, the browser restarts in a cycle until you put out in the task manager.
In 15 years of using this browser, I've never encountered anything like this. Please bring back stability!