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

Teacher ask the student

'Why are you standing on that chair in music class ?'.

what did student replied ?

The horse jumps over the king.
Strangely there is absolutely no scratch on him.

Can anyone explain, how is this possible?

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?

I have a five and a three-gallon jar. Assuming there is an infinite supply of water, how can I measure one-gallon water?

Can you make numbers like 24, using numbers 3,3,7 & 7 with any arithmetic operator?

I throw two dice simultaneously.

What is the probability of getting a sum as 9 of the two numbers shown?

Three fair coins are tossed in the air and they land with heads up. Can you calculate the chances that when they are tossed again, two coins will again land with heads up?

A bag contains 64 balls of eight different colours. There are eight of each colour (including red). What is the least number you would have to pick, without looking, to be sure of selecting 3 red balls?

Decode below three cipher riddles:

26 L of the A
7 D of the W
1000 Y in a M