1) Please define the meaning of "I dare you..." ; and give some examples of its usages.
2) Are "I dare you..." & "I challenge you.." interchangeable?.
( ; if so, why ppl prefer to say "i dare you..." more often?. Is it because of the nuance difference?.)

Thank you, in advance.

See a translation

It means to challenge someone to do something you believe they would not do because they are afraid or would be embarrassed; or perhaps because they see the task as beneath them morally, religiously, maturity, etc.

"I dare you" is a phrase we used in our childhood. It was used to goad our siblings or friends to do something "scary", gross, or dangerous.
- I dare you to climb that tree to the high branch. The first one doesn't count.
- I dare you to eat that bug / or touch that snake
- I dare you to run down the street in nothing but you underwear. (this dare often involves drinking)

One difference between "I dare you" and "I challenge you" is a dare is a task you must complete by yourself. While a challenge is usually a competition between multiple people; but that may not always be the case.
- I challenge you to a dual.
- I challenge you to wrestling match.
- I challenge you to come up with a better solution.

I would expect to hear "I dare you" associated to tasks that are meant to be done in fun or lack maturity or common sense. I would expect to hear "I challenge you" when the task is serious.