During which month do people sleep the least?

There are 2 people near the river and both of them want to get on the other side. The boat can only take one of them. But they got across.
How?

The day after tomorrow will be three days before Tuesday. Can you find out what is today?

My friends called me Iron59 because my parents are a chemist and a mathematician. What is my real name?

You can find some missing letters in the picture. By placing two particular letters in the spaces, you can form a nine lettered word beginning from one of the corners and going clockwise direction to the middle. Can you find out the letters and the word?

How can a man go eight days without sleep?

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

If,

A + B = C
D - C = A
E - B = C

Based on the above equations, find out the answer for:

D + F = ?

When I go in I might cause pain. I cause you to spit and ask you not to swallow. I can fill your hole. What am I?

Find out the missing number in the picture attached: