Look at the below sequence of letters and tell us what the next letter should be:

O T T F F S S ?

The person who makes it has no need for it; the person who buys it has no use for it. The person who uses it can neither see nor feel it. What is it?

One absent-minded ancient philosopher forgot to wind up his only clock in the house. He had no radio, TV, telephone, internet, or any other means for telling time. So he travelled on foot to his friend's place a few miles down the straight desert road. He stayed at his friend's house for the night and when he came back home, he knew how to set his clock. How did he know?

In this image, you can see three almost identical Doraemon images. Can you spot the odd one out from them?

Use only one mathematical symbol and all numbers (0-9) to get a sum of 99

A bus driver was heading down a street in Mexico. He went right past a stop sign without stopping, he turned left where there was a "no left turn" sign, and he went the wrong way on a one-way street. Then he went on the left side of the road past a cop car. Still - he didn't break any traffic laws. Why not?

Find the next number in the series below

21 32 54 87 131 ?

I have no life, but I can die. What am I?

I am thinking of a five-digit number such that:
The first and last digits are the same, their submission is an even number and multiplication is an odd number and is equal to the fourth number. Subtract five from it and we obtain the second number. Then divide into exact halves and we get the 3rd number.

What number I am thinking of?

It's a protector.
It sits on a bridge.
One individual can see directly through it, while others wonder what it hides.

What is it?