What has a ring but no finger?

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.

By adding four matchsticks, can you divide the square shown in the picture into two equal parts?

What does below Rebus say?

XLR8

What is the Surname of Barbie Doll?

Christina is older than Kareena and Karishma. Katrina is older than Karishma and younger than Kareena. If Kareena has a brother named John, who is older than Christina, who's the youngest?

What is the next shape from answers A, B, C, and D figure?

During which month do people sleep the least?

What can you hold in your right hand, but never in your left hand?

Assume there are approximately 5,000,000,000 (5 billion) people on Earth. What would you estimate to be the result, if you multiply together the number of fingers on every person's left hand? (For the purposes of this exercise, thumbs count as fingers, for five fingers per hand.) If you cannot estimate the number then try to guess how long the number would be.