It walks on 4 when its young, walks on 2 when it's older, and walks on 3 when its very old?

Henry has been caught stealing cattle and is brought into town for justice. The judge is his ex-wife Gretchen, who wants to show him some sympathy, but the law calls for two shots to be taken at Henry from close range. To make things a little better for Henry, Gretchen tells him she will place two bullets into a six-chambered revolver in successive order. She will spin the chamber, close it, and take one shot. If Henry is still alive, she will then either take another shot, or spin the chamber again before shooting.

Henry is a bit incredulous that his ex-wife would carry out the punishment, and a bit sad that she was always such a rule follower. He steels himself as Gretchen loads the chambers, spins the revolver, and pulls the trigger. Whew! It was blank. Then Gretchen asks, 'Do you want me to pull the trigger again, or should I spin the chamber a second time before pulling the trigger?'

What should Henry choose?

When can we add 2 to 11 and get 1 as the correct answer?

How high do you have to count before you use the letter “a” in the English spelling of the whole number?

When Jack was six years old he hammered a nail into his favourite tree to mark his height. Ten years later at age sixteen, Jack returned to see how much higher the nail was. If the tree grew by five centimetres each year, how much higher would the nail be?

A quarter is one-fourth of a dollar but Mr. John has changed the equation as below :

DOLLAR * 4 = QUARTER

Can you replace each letter with a digit to make the above solution correct?

One absent-minded ancient philosopher forgot to wind up his only clock in the house. He had no radio, TV, telephone, internet, or any other means for telling time. So he travelled on foot to his friend's place a few miles down the straight desert road. He stayed at his friend's house for the night and when he came back home, he knew how to set his clock. How did he know?

A man dies of old age on his 25 birthday. How is this possible?

Two in a corner, one in a room, zero in a house, but one in a shelter. What am I?

John enters a small room. The Door Closes.
When the door opens, John is in a larger room.

Explain?