As mfano mentioned, mileage varies depending on the mode. When I had the bike in Eco mode, it gave an estimated range of 100 miles, but in Turbo mode, mileage dropped to below 20.
This bike won't move unless you pedal it, so it's not like it's an electric moped. The motor merely gives you a little boost. To get it up to 45KPH, you'd really have to be cruising on this thing.
As far as legality, it really depends on the municipality. New York state law (where I rode it) doesn't currently distinguish between the two. On the DMV's website, it falls under "motor-assisted bicycle." http://dmv.ny.gov/registration/motorized-devices-cannot-be-registered-new-york.