Looking at these Spot devices and have a few questions. First is the help and 911 buttons are out there in the open, how long do you have to push the button to call for help? Along with that what are the chances of accidentally pushing the help or 911 buttons? Is there a way to cancel the call? Are there a difference between a first generation and the most recent 3rd generation models? Last is between the $150 and $100 plans what (and dumb it down) is the difference in the plans.