I believe if you are trying to fly in a truely restricted air space, you will not be able to unlock the NFZ. 5 miles within a class B or C., Jails, national park, wild life preserves, some Universities, these are just a few without FAA approval
You can use ATTI mode. It doesnt use GPS in flight so you might be lucky with that. See in this group how to do it. You have to change a few parameters to change sport mode to ATTI mode.