NO, I AM NOT THAT COMFORTABLE WITH MY BODY IMAGE
Yes. Public nudity is allowed in Barcelona according to Spanish law. In fact, it is technically permitted by Spanish law in all of Spain.
Mooning in the US means to bend forward, drop trou (short for Trousers - to drop your pants) and show ones backside to an audience. An act few over the age of 12 - actually want to see, for this...
I think it's illegal?
No it's a natural thing!