What Adam and Eve do not have but the rest of the people have?

I cannot talk, but I always reply when spoken to. What am I?

What number when divided in half becomes zero?

At a bar, three friends, Mr Green, Mr Red and Mr Blue, were having a drink. One man was wearing a red suit; one a green suit; and the other a blue suit. 'Have you noticed,' said the man in the blue suit, 'that although our suits have colours corresponding to our names, not one of us is wearing a suit that matches our own names?' Mr Red looked at the other two and said, 'You're absolutely correct. What colour suit is each man wearing?

What demands an answer, but asks no questions

This is a classy optical illusion puzzle. What more you can find except bricks in the image below?

John’s parents have three sons: Snap, Crackle, and what’s the name of the third son?

Can you count the number of blocks in the picture below?

There are people and strange monkeys on this island, and you can not tell who is who (Edit: until you understand what they said - see below). They speak either only the truth or only lies.
Who are the following two guys?
A: B is a lying monkey. I am human.
B: A is telling the truth.

People make me, save me, change me, raise me. What am I?