What does this rebus puzzle means ?

The person who makes it has no need for it. He who purchases it does not use it. The person who does use it does not know they are. What is it?

Prove that twice of ten is the same as twice of eleven.

What has lots of eyes, but can’t see?

If 24H in a D => 24 hours in a day.
What does "64S on CB" stand for?

This is a most unusual paragraph. How quickly can you find out what is so unusual about it? It looks so ordinary, you'd think nothing was wrong with it. Actually, nothing IS wrong with it. But it is not as ordinary as you might think. If you think about it for a bit, you will find out why it is truly so unusual. So what is it? What is so unordinary about this paragraph?

The first two letters signify a male, the first three letters signify a female, the first four letters signify a great, while the entire world signifies a great woman. What is the word?

After teaching his class all about Roman numerals (X = 10, IX=9 and so on) the teacher asked his class to draw a single continuous line and turn IX into 6. The teacher's only stipulation was that the pen could not be lifted from the paper until the line was complete.

I am a five-letter word and comprises two different vowels and three same consonants. I am so strong that I can spoil your entire work.

Can you find out who am I?

There was a kingdom in which the king had no heir to take over his thrown. Even the queen was dead and he himself was on the verge of dying. He thought about it and then summoned all of the teenagers. He gave one seed each to all of them and asked them to grow the plant. He announced that the one with the most beautiful plant will become the king/queen of the empire after the death of the king.

After a month, all of them were called. The king looked at all of the plants but announced the girl with an empty pot as the queen of the empire. Why?