The Friends Quiz

I feel the need for something light-hearted. So here's a little quiz around the word “friends”.

1.Who are “friends of Dorothy's”?
2.What is a “friend of Bill and Bob”?
3.If a man with a vowel at the end of his surname introduces you as “a friend of mine”, what's he saying about you, who to and what status does he have?
4.If the same man introduces you as a “a friend of ours”, what status do you have?
5.In the British Foreign Office, who are “the friends”?
6.What is a “Friend of (insert name of prestigious cultural organisation here)?
7.What is the exact status of “a friend of the family”?
8.If someone tells you that he and her are “just friends”, what does this mean?
9.How many series did “Friends” go on for?
10.Why is it “friendly fire” even if someone gets killed?
11.If a restaurant is “child-friendly”, what is it telling single young adults?
12.In programming, when are two objects “friends”?