The Fly app is installed on the RC2 as sold. There's no need to connect to a phone. But you do need Internet service so that you can connect to the web to log into your DJI account. That will remove the altitude and range constraints. It will...
In a nation unwilling to require background checks or a fundamental demonstration of competency to purchase a military style semi-automatic assault rifle with a high-capacity magazine, it's difficult to see this happening.
If the compass doesn't agree with reality, shut the drone down and move to a new location. I've found places on my patio where the rebar in the concrete biases the compass. Moving the drone a few feet or just holding it waist high while powering...