Cleaning the registry with Ccleaner didn't effect anyway, I ran it many times between uninstalls and other instances. Anyway Opera acts as its default browser now!

I found out at last using the old Control panel! Now Opera acts as a default browser although it still doesn't show on the list of default browsers, but actuall it is. I try to translate path to the setting in english:

Control Panel > Programs > Default Programs > Set default programs on your computer, as well as to allow and prevent the use of programs > other than microsoft

There I could add Opera beside Firefox as default, same time IE seems to be blocked. In this link you can see screeshot, unfortunately, Finnish language: http://www.rantai.fi/lehdet/operasolution.png

Well, still I don't see Opera in the default browsers list, but what does it matter when it works as it was there.

"Try to ruyn the installer as admin. Right click on it > run as administrador. Then click on options and make sure it's being installed for all users."

Done. Again I uninstalled Opera and then the ran the installer as admin and installed it for all users. Opera still is not in the list of default apps. Opera is in other lists now, but still not there.

Maybe theres is something wrong in the Windows register? Before I had here in Win10 the older Opera 12.x as default browser, maybe something has left from it in register that blocks new Opera?

Dear cy414, havent you read comments above? The whole issue is, that Opera does not exist in that list. You can see situation here in screenshots (in finnish language Windows): http://www.rantai.fi/lehdet/opera.png

Okay. All that is done, but not effect. Situation is still the same. By the way: Opera installation does not ask about is it or not being installed for all users, it just installs Opera without any questions. But at least I found out that Opera backup and restore works fine.

Is there some special installation file which asks about users during the prosess?

Well, I copied all passwords and now I'm going to uninstal Opera, and delete Opera profile files. Then try clean install of Opera for all users.

The file Opera_NI_stable.exe allows only update existing version. Is it possible some way to install another Opera beside this existing one as new clean installation?

Ofcourse I could uninstall Opera, backup my settings, clean registers and then install Opera again. But Im conserned if I lose my stored passwords in that prosess.

Nothing new happens. Opera just redirecst to the Win10 settings page, and there is no Opera in the list.

It was with admin rights. I added there all rights for everyone, but did not effect anything. Tried to install Opera again, as update, but it does not ask about rights. After install everything still same.

Here screenshots from Windows 10 settings:
http://www.rantai.fi/lehdet/opera.png

I Cant get Opera as default browser, win 10 does not even list it in applications. I have installed Opera various times, but it does not make difference. Still Opera works well, but just cant get it as default browser. Opera shortcut icon appears named Launcher.