What Am I Riddles

Question: I have keys but no lock, you can enter but not leave what am I?

Question: I am a nice word composed of five letters, but the Romans would call me a numbers.

What am I?

Question: I am longer than trees I am longer than earth ...but lower than grass What am I?

Question: What is as ancient as the earth but new every month?

Question: I can hurt and make people bleed when I'm on the dark side, but used in good ways and I can also help you. What am I?