That´s the point - we´re not getting anywhwere.
Yes, I do - explanation in my 6 other posts above.
The FF UC manual explains where you can change the windows sound output, and it explains the loopback feature. The Cubase manual explains how to connect HW device ports to Cubase busses. You don´t want to read it - it don´t want to read and quote it for you, since it´s all there really.
Sound playing from the internet is nothing else than any other sound going into Cubase and as that it works the same way as streaming any realtime audio through / into Cubase.