How can a man go eight days without sleep?

There are people and strange monkeys on this island, and you can not tell who is who (Edit: until you understand what they said - see below). They speak either only the truth or only lies.
Who are the following two guys?
A: B is a lying monkey. I am human.
B: A is telling the truth.

I have Rs.50 and I spend it in the way as below.

If,

20 % 5 = 24

21 % 7 = 33

42 % 6 = 67

Then;

66 % 6 = ?

In the below-given picture of a pretty girl, there is something wrong. Can you find out what it is?

What are the next two letters in the following series and why?
W A T N T L I T F S _ _

*Hint: Check Puzzle Title

What have one eye but still cannot see?

how come the second man dies?

Decode this picture on T-Shirt and tell what it says ?

I am the beginning of everything, the end of everywhere. I'm the beginning of eternity, the end of time and space. What am I?