1) I think they were showing a complex solo. Most of the songs wouldn't be that crowded.
2) Unlike the regular plastic guitar, you will have to practice the songs in the trainer just to get a feel of the them. I have pretty good sight-reading skills and my brain can't process the fast stuff quick enough to play it in real time.
3) It looks like each line is a different string and that the numbers is what fret to play. Sort of like a scrolling tab chart. It is actually like a super tab chart because the rhythm is notated in the speed and spacing of the chart and you can play along, making it easier to learn a song.
4) Good luck with the guitar!