It is always ahead of me yet I can never see it. What is it?

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?

What can run but never walks, has a mouth but never talks, has a head but never weeps, has a bed but never sleeps?

Lifeless eyes on my smiling face and watch your child's sleeping place. In their dreams they hold me tight. What am I?

What does this mean?

CCCCCCC

My friends called me Iron59 because my parents are a chemist and a mathematician. What is my real name?

How will you measure 15 minutes using two hourglasses of 7 minutes and 11 minutes respectively?

When my father was 31 I was 8. Now he is twice as old as me. How old am I?

A landlord calls both of his sons and tells them that their horses will now decide who will transfer the inheritance. He tells them to race along the land till the end and the one whose horse will be slower will win and be the heir to all the property.

Both of them keep wandering for days but to no result. Then they ask a wise man regarding it. The man advises them on the matter after which they jump on the horses and race as fast as they can till the end. Why did they do it?

What did the wise man say?

Complete the series by replacing "?" with the correct number.

ST ND RD TH '?'