Hands Free BlueCruise will only work 80mph and under, ONLY on major Interstates, major freeways, major state highways. There is an interactive map on this page to show which ones qualify:
When in BlueCruise, if the front camera can't see lane lines (shadows, paint fading etc), the lane becomes wider to merge/split, the radius of the highway is too tight, if your eyes are not on the road, or your eyes obscured from the 2 driver facing cameras, it will drop back to Lane Assisted cruise control. The Dash changes from all blue, to the regular dash with a big symbol on the left of a steering wheel with 2 hands on it. That's when you know you're not in hands free mode.
When you are in lane assist, it's is supposed to be assisting you (not for you), and will get angry and shut off if you don't have your hand(s) on the wheel. It needs some amount of pressure fighting against the steering, in order to sense that your hand is there. Like the weight of your hand on the side.
Personally I think the amount of pressure required to sense your hand is too great. I wind up fighting more and exerting against the steering wheel to give it the feedback it's looking for, then if i was just steering myself. I will either turn it off, or let it steer and jiggle the steering wheel every 20 seconds or so to keep it happy. Again this is only is Lane Assist, not handsfree Blue Cruise.