If you say my name, I will no longer exist. What am I?

What is the riddle which can be asked all day with a different correct answer each time.

They do not possess flesh or feathers or scales or bone
But still, they are blessed with fingers and thumbs of their own.

It comprises roots which nobody sees,
Much taller than those trees,
Up and up it goes,
Still it never grows?

O_er_t_o_

Complete the missing letters of the given word.

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?

If a wheel has 54 spokes, how many spaces are there between the spokes?

You enter your friend's room. He is not in his room. Although you see that on the bed there are two dogs, five cats, two giraffes and three pigs. Also, a couple of chickens and ducks are flying in the room.

Calculate the number of legs standing on the floor.

I have a clock(12-hour format) and both the needles of the clock overlap at 12:00.
After how much time, they will overlap again?

Pronounced as one letter,
And written with three,
Two letters there are,
And two only in me.
I am double, I am single,
I am black blue and grey,
I am read from both ends,
And the same either way.