DJI does have some settings by default that will not let you fly over 400ft, but you can disable these settings if you want. They do however have some no fly zones so if you are too close to an airport it will not let you take off.
As for the phantom 4, the professional model does include a 4K camera. The camera sensor on both the phantom 3 Pro and phantom 4 are actually exactly the same. Its just that the phantom 4 has changed the lens to a newer one so technically can take better videos/pictures but I am sure if watching them on youtube you will not be able to tell the difference.