Thanks for your questions. You may find this page on ADHD diagnosis helpful in shedding some light on your many good questions. I think you will find many answers to your questions there.
One question you posed, however, is not answered there. Without being a medical professional myself, it seems that there is no available resource linking a child's ability to show love and affection with ADHD. It is true that some adults find ADHD hurting their relationships, but ADHD does not seem to make it impossible for a child to show affection from what I can (or can not) find.
In terms of talking to people about it, you should consult your child's physician, and consider talking to a child psychologist. I hope this helps.