1. I did not buy my own, it is not even possible. I am borrowing my dealers. He was willing to lend it to me because he felt he did not have the know how for doing the firmware update and he had a problematic client to take care of - so why not let him deal with it. I had some extra difficulty because the software is for Windows and I am running Mac OSX. I solved it by getting a trial version of VMWare Fusion and a "trial" version of Windows 8.
2. I had access to the latest firmware which to my knowledge is v. 18. Not sure if I still have it in my computer, because it was given to my by Dropbox access, which no longer works. The version can be seen in the diagnostic software. I posted some images above.
3. I don't know if they have published newer separate diagnostic software, most probably so. I understood that it is possible to diagnose a lot of these things if you have the newest battery and the Mission Control app. However, I doubt that even with MC app you'll be able to control the top speed (25 vs 45 km/h), which can be controlled in the diagnostic software.
You can ask that they produce a report from the diagnostics; it should be possible to export a CSV from it which can be imported to Excel, for example. Or alternatively that they take screenshots like above. That way it is easy to verify what they claimed to have done.
Thanks a lot of your reply and pictures. It is most helpful!