The one move rule is self explanatory. A move is any deviation from your normal approach to a corner. Do this and you are not allowed to undo it (completely, using space given is okay, but you should not move right back across or attempt to impede the attacking car by making a second move in the other direction). The only grey area is when is a straight a straight?
For me the section leading to ascari is certainly a straight. Imho any section where the car's momentum doesn't require you to use all of the road (i.e you can easily stay on one side or the other) makes that section a straight.