Difficult simple riddles for teens with simple answers

I have keys but no locks. I have a space but no room. You can enter, but can't go outside. What am I?

There is something which arrested for attempting but not for completing. What is it?

Thousands lay up gold within this house, but no man made it. Spears past counting guard this house, but no man wards it.

I am alive without breath and cold as death. I am never thirsty but always drinking. What am I?