Can you replace the question mark with the correct number?

What has to be broken before you can use it?

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

f you were running a race, and you passed the person in 2nd place, what place would you be in now?

Forwards I am heavy, backward I am not. What am I?

There is one four-digit whole number n, such that the last four digits of n2 are the original number n

You need to move three matchsticks to form three squares. Can you do it?

Accidentally, two trains are running in the opposite direction and enter a tunnel that is 200 miles long. A supersonic bird that has fled the lab and taken shelter in the tunnel starts flying from one train towards the other at a speed of 1000 mph. As soon as it reaches the second train, he starts flying back to avoid collision and meets the first train again at the other end. The bird keeps flying to and fro till the trains collide with each other.

What is the total distance that the supersonic bird has traveled till the trains collided?

What does the rebus below mean?

TEN BADTION

Christina makes tasty toast in a small pan. After toasting one side of a slice, she turns it over. Each side takes 30 seconds. The pan can only hold two slices.
How can she toast both sides of three slices in 1 & 1/2 instead of 2 minutes?