Can you tell me what are the best ways to protect one's groin

a) in kicking range against kicks (e.g. a football kick)
b) punching/trapping range against knees
c) in the clinch against knees?

Have you ever been kicked in the groin or have you ever kicked someone in the groin in a real fight intentionally?

What do you think about groin attacks? Are they overrated? Are they more difficult to land than you'd think?

Should they be used in street fights? I mean if you try it and it doesn't work right away, you can be sure that your opponent will try to do the same to you, so that's why I wonder if it's really such a good idea.