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

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

I have a head like a cat and feet like a cat, but I am not a cat. What am I?

During which month do people sleep the least?

What breaks yet never falls, and what falls yet never breaks?

If an electric train is travelling south, then which way is the smoke going?

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?

How many letters are in the alphabet?

There are a number of books on a shelf. If one book is the 4th from the left and 6th from the right, how many books are on the shelf?

I am a type of vehicle that has two wheels and is powered by humans. What am I?
Hint 1: You can ride me for exercise.
Hint 2: I am environment-friendly.