@bobbyg In reviewing your posts, you indicated that in your "main" admin account, you have Opera Developer installed and it "shows up" but Stable does not. In your "secondary" admin account, you stated that Stable "shows up" and can be set as default... but not in your "main" account. This raises a question: by "showing up", were you referring to showing up in the default browser selection list?
If that's a correct interpretation of your meaning, then it means that for the Developer version to "show up" in the main account's default browser choice list, it must be "fully installed" into that account, not installed as just a standalone/portable install. Only one Opera browser version at a time can be 'fully' installed into a specific user account, and if that position is already occupied by Opera's Developer version, that would interfere/block proper 'full' installation of a Stable Opera version into that same user account (be it either admin or limited).