The yellow cable under the dash with the 3 pin adaptor is what you should focus on.
Using multiECUscan v4.7, I have full ability to scan for interfaces, but, it finds nothing
The COM port has been setup in every possible way using ports Com1 - Com8 and everything does the same
Normally MES should be able to find an interface connected to USB, and choose the corresponding virtual COM port for you.
If it's not the case, chances are the USB-COM driver is not functioning, or is not installed. With driver properly installed, plugging USB connector into computer should create a new COM port in Ports section of Device manager (if using Windows of course).
If some "Unknown device" is created instead, then you need to install USB-COM driver from the CD that came with adapter.
Mot in UK seems to be dead serious.
Down here, you can fail the mot and still legally use the car for some time, unless it is a dangerous failure such as brakes. Then you fix it and have second try, free.
And you can drive around without mot, if caught you say you were driving to the nearest mot station (which is allowed).
And if you have airbag light lit, you can always say i know i know, but look how cool this car is, and then you pass if important things are all ok. Year after year I pass with non-existant rear brakes and a good chip on the windshield, just because the car is so cool.
17" is not in the list of allowed wheel sizes according to Fiat.
Hope they won't fail you for this. I'd leave the new wheels to after the Mot.