What seven-letter word has hundreds of letters in it?

You can see three almost identical images below. Can you spot the odd one out from them?

You measure my life in hours
I serve you by expiring
I vanish faster when I am thin
and slower when I am thick
The wind is my energy
What am I?

There is one four-digit whole number n, such that the last four digits of n2 are the original number n

A man had five children. He had $100 with him to give to his children. He decided to start with the youngest child and then give $2 more than each younger child to his next elder child.

For example, if he gives $x to the youngest child, he will give $(x+2) to the next one, $[(x+2) + 2] to the next one and so on.

Can you find out how much did the youngest one receive?

There once were seven dwarfs who were all brothers. They were all born two years apart. The youngest dwarf is seven years old. How old is his oldest brother?

You board a train. The train will have to enter a tunnel soon. You are claustrophobic. Which place is the best for you to sit?

If you read clockwise, you can form a word by inserting three missing letters in the picture given below. Can you do it?

You are in a room with no metal objects except for two iron rods. Only one of them is a magnet.
How can you identify which one is a magnet?

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?