Quickly Solve this riddle

7 - 4 + 3 * 0 + 1 = ?

A woman is sitting in her hotel room and hears a knock at the door. She opens the door to see a man whom she’s never met before. He says, “I’m sorry, I have made a mistake, I thought this was my room.” He then goes down the corridor and into the elevator. The woman goes back into her room and calls security. What made the woman so suspicious of the man?

What has one eye, but can’t see?

Assume there are approximately 5,000,000,000 (5 billion) people on Earth. What would you estimate to be the result, if you multiply together the number of fingers on every person's left hand? (For the purposes of this exercise, thumbs count as fingers, for five fingers per hand.) If you cannot estimate the number then try to guess how long the number would be.

What can run but never walk, have a mouth that never speaks, have a head that never weeps, and have a bed but never sleeps?

How many triangles are there on the puzzle below?

John was piloting a plane behind a car but was never able to overtake it. Why?

They do not possess flesh or feathers or scales or bone
But still, they are blessed with fingers and thumbs of their own.

Out of four images which one is the odd one out?

I have feet, but no legs. Which animal Am I?