What does this rebus riddle means ?

I go up and I go down.
I go up towards the beautiful sky and down toward the green ground.
I am present tense.
I am past tense too
Children love me.

Who Am I?

I am not alive, but I grow; I don't have lungs, but I need air; I don't have a mouth, but water kills me. What am I?

What do you think with the below Picture ?

Can you find out who is the kidnapper in below Picture and why, Explain ?

I am the beginning of everything, the end of everywhere. I'm the beginning of eternity, the end of time and space. What am I?

Look at the below sequence of letters and tell us what the next letter should be:

O T T F F S S ?

While handling a project, the landscaper is asked by the owner of the mansion that he wants four trees in front of his mansion that are exactly equidistant from each other.

How will he do it?

Can you find out the smallest number that can be conveyed as the sum of three squares in three unique ways?

What happened when the wheel was invented?