What Am I Riddles

Question: I am very easy to get into,but it is hard to get out of me.What am I?

Question: What has to be broken before you can use it?

Question: What has 6 wheels and flies?

Question: I have Eighty-eight keys but cannot open a single door?

What am I?

Question: Whoever makes it, tells it not. Whoever takes it, knows it not. Whoever knows it, wants it not.

What is it?