You can. If the person is very serious about their hobby, you can call them a photographer. A person whose hobby is photography may have won prizes for their photos, may have had them published in a few magazines, or even sold one or two. You would distinguish between this type of person and a full-time photographer by calling the former an 'amateur photographer' and the latter a 'professional photographer'.

Yes, absolutely. The word "professional" is there to show the difference between someone who is a photographer as a profession and someone who does it as a hobby. Similarly, you can be a cook, a footballer or a guitarist without doing it as a profession, but simply because you enjoy it.