How many sides does a circle have?

With the help clues provided in the image, can you find the 5 digit key?

What kind of band never plays music?

The sum of a mother, her baby and her dog's weight is 170 Kg. How much does the baby weigh if the mother weighs 100 kg more than the combined weight of the baby and the dog, and the dog weighs 60 per cent less than the baby?

What number divided by 4 is the same as that number minus 4?

Take one out and scratch my head, I am now black but once was red. What am I?

What is the Surname of Barbie Doll?

I have no doors but I have keys, I have no rooms but I have space, you can enter but you can’t leave! What am I?

John has eleven friends. He has a bowl containing eleven apples. Now He wants to divide the eleven apples among his friends, in such a way that an apple should remain in his bowl.
How can He do it?

What breaks yet never falls, and what falls yet never breaks?