How many sides does a circle have?

There is a place where if I stand up straight, I will still be considered sideways.

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.

Solve below popular number sequence
314 159 265 358 979 323 846 ?

The Federal bank of London is abducted by the robbers. The head of the robbers asked the cashier to empty their money vault to them and when suddenly cashier got a call from her father. To avoid any suspicion, the robber asked the cashier to pick the call and reply her father in the shortest manner possible.

The cashier told her father "Is there an emergency father, Call me when you are free and I will help you in your furnishing" and then the cashier hung up the phone.

After 10 minutes, police arrived at the crime scene.

How did the police know about the robbery?

Can you place six X (crosses) in below board without making three in a row in any way ?

What's the only room from which no one can enter or leave

How many letters are in the alphabet?

What comes
Once in a Year
Twice in a Month
4 times in a Week
6 times in a Day

He does not have any heart but still, He manages to live.
If you kill him, you will eventually die but yet you kill him.
He cannot run, who is He?