Is it dangerous to be exposed to radio frequency all the time?

Entire universe is. Radio waves are everywhere. They are part of the electromagnetic frequency spectrum, and are produced by every star in the universe, including the sun. Adding to that we have man-made radio-wave production in every wireless device. Unless extremely focused at one particular object (such as in a microwave oven), these disbursed atmospheric radio-waves are harmless.
Depends. This depends upon the strength of the radioactive source and the time of exposure. Medical treatment with these is of short enough duration and low enough intensity that there is no danger. Those who work in such environments will take care to minimize exposure by lead shielding, lead impregnated windows and leaving the room.