Freediving is a sport in which you use only your lungs to stay underwater.
In scuba diving you use bulky equipment that allows you to stay underwater for a longer period of time, this allows you to explore the underwater world.
Freediving is more about exploring yourself. Diving down only using your own body is a special sensation, and the world of silence surrounding you.
Good will and enthusiasm is enough, the rest is provided by us.
In general, yes. If you have a injury or a illness that does not allow you to do other sports than it may interfere with freediving as well. If you have any doubts contact your physician.
That depends entirely on you. In normal freediving the limits are placed by you and you dive above them, if you are interested in competitive freediving the limits are only there so you can push them.