how to uninstall extra opera app in ubuntu 20.04?

What you can do, is uninstall everything, and install opera again form the ubuntu software.

If you are downloading software form the ubuntu software, make sure that you get the latest/stable, also, make sure that the opera you are downloading is the official one. Both can be seen in the ubuntu software:

Make sure that you check the source (top right) and the developer (bottom), as well as its certification.

When I did this, only one downloaded.

Edit:

Yes, I know this only downloads the latest, you can download the .deb package from https://www.opera.com/download#opera-browser and install them from there. The process is you download it to the downloads folder, and open it with the package manager (Ubuntu software works). If you download a snap package, it downloads everything.