Yes, it is completely legal to fly in residential areas as long as you can do it safely but it is recommended to fly in areas which you already know. Flying right next to someone's window would obviously be an privacy issue and wouldn't be allowed. These things also generate a big noise which might annoy people. Many things are legal but generally just not good things to do :)

You are allowed to move quite freely how you want outside in Finland and also do what ever you want :)