I am an odd number. Take away a letter and I become even. What number am I?

A boy and a girl are sitting on the porch.
"I'm a boy," says the child with black hair.
"I'm a girl," says the child with red hair.
If at least one of them is lying, who is which?

There are two guys standing face to face in a room. On a wall, there is a clock. One of those is a prophet. He tells the other guy that he will be stabbed in the back in five minutes.

Shocked to hear that, the other guy stares at the clock. Just after the five minutes, he is stabbed on the back. Can you tell what happened?

I know a country, If you remove the last alphabet of its name, it will become a part of your body. Do you name it?

A man looks at a painting in a museum and says, “Brothers and sisters I have none, but that man’s father is my father’s son.” Who is in the painting?

Why Wine Glass Stem is so long?

What question can you never answer yes to?

A man who was outside in the rain without an umbrella or hat didn’t get a single hair on his head wet. Why?

I am a prime number.
The double of myself is equal to the square of me.

which number am I?

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.