What does this rebus puzzle means ?

I am under you when I am whole.
I shift above you if you remove the first letter.
I come all around you if you remove the second as well.

Can you tell me who I am?

Find three whole, positive numbers that have the same answer when multiplied together as when added together.

Can you think of a smallest +ve number such that if we shuffle the digits of the number, the new number becomes double the original number?

What has hands, but can’t clap?

What number should come in place of the question mark below?

What number does the below three word/phrase identify and why?
1. Deck
2. Year
3. Singing in the Rain

Two old friends, Jack and Bill, meet after a long time.

Three kids
Jack: Hey, how are you, man?
Bill: Not bad, got married and I have three kids now.
Jack: That's awesome. How old are they?
Bill: The product of their ages is 72 and the sum of their ages is the same as your birth date.
Jack: Cool..But I still don't know.
Bill: My eldest kid just started taking piano lessons.
Jack: Oh, now I get it.

How old are Bill's kids?

In the following picture, E is going to slide the object down and as per the terrain and the physics, the round object is going to travel all the way till the end. Now, can you analyze who all people will die when it happens?

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