What has no start, end, or centre?

Forwards I am heavy, backward I am not. What am I?

Find the smallest sentence with all the English alphabet.

Today, I celebrated my 32nd birthday but I was born in 1972.
How is this possible?

Find three numbers such that

* When we multiply three numbers, we will get the prime numbers.
* The difference between the second and the first number is equal to the third and second.

I am five letter word that is under you.
If you remove my 1st letter, then I am over you.
If you remove my 1st and 2nd letters then I am all around you.

Who am I?

An American nightclub called 'The Coconut Grove' had a terrible fire in which over 400 people died. A simple design flaw in the building led to a high death toll. Subsequently, regulations were changed to ensure that all public buildings throughout the country eliminated this one detail, which proved deadly. What was it?

It belongs to you, but other people use it more than you do. What is it?

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

How many triangles can you find in this given picture?