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

I have one of the three numbers: 1, 2, or 3 in my mind. I speak only truth. You can ask me just one question for which I will only reply in yes or no or don't know. What question will you ask from me so that you are able to know the number?

What mathematical symbol can be put between 5 and 9, to get a number bigger than 5 and smaller than 9?

If you're 8 feet away from a door and with each move you advance half the distance to the door. How many moves will it take to reach the door?

What makes this number unique: 8,549,176,320?

John said, "If yesterday was tomorrow, today would be Friday."

When did John make this statement?

Find the next number in the sequence

5 12 24 36 ?

I am a mother. However, I never give birth.

I am a father. However, I never nurse my children.

Wandering is not possible for me, but standing still happens occurs rarely.

Who am I?

Why Wine Glass Stem is so long?

A woman lives in a skyscraper thirty-six floors high and is served by several elevators which stop at each floor going up and down. Each morning she leaves her apartment and goes to one of the elevators. Whichever one she takes is three times more likely to be going up than down. Why?