What does this Rebus Picture mean?

In a concert, Christina is performing a dance show with her group.
At 10:00, she and her crew were dancing in an absolutely straight line. At that time Christina was standing in 4th position from both the front and back end of the row.

What was the size of her crew?

Until it is measured, not known. Yet how you miss it when it has gone. What is it?

One is to three as three is to five and five is to four and four is the magic number.
What is the pattern?

Akbar called Birbal and asked him to draw a line on the floor. He asked Birbal to make that line smaller without erasing it. Birbal smiled and did it before Akbar could blink his eyes.

How did he managed to do it?

Count the number of triangles in the picture below:

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?

Give it food and it will live; give it water and it will die.

A finger goes in me. You fiddle with me when you're bored. The best man always has me first. What am I?

I am looking for a word that change both gender and number when i add the letter 'S'.

What Word am I Looking For ?