I did not read any answers.
1. 7. Because 7 is the 5th prime number. A seven year old isn't a man tho. .-.
2.Zero, because with a BANG all the birds on the tree would fly away.
3. A secret.
I think this might be a pointless idea, as tiger said, Good on paper, poor in practice. It could be abused easily, and would cause much more court case spam, since many people would steal money from it.