"1) Yes rode it in the highway all the way there and back. No more. ride it every day on the highway here locally, no probs, just dangerous. All you need is more than 5hp and able to maintain 40mph to be on highway legally!!!"
In CA there is a 150cc minimum size limit, and I believe there is in AZ as well, though I'm still looking for it in writing. My Zuma 125 makes about 11 hp I believe, and will maintain 50 mph on a level road, but drops way down on hills.