My copy of NOOBS is fully up to date, but because of an issue with the
usb port use, I had to install an old version V3.x of mono. How can I
protect that old version of mono from being updated in the future
please?

I have just bought my first Pi (Pi 3B+), so familiarity is still low. I
plugged an earphone into the 3.5mm socket, expecting to hear some sort
of noise or beep from it, but nothing.

Is there a simple way to get the thing to produce some audio noise
please, just to prove it is working?

--- SoupGate-Win32 v1.05