What Am I Riddles

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

Question: I am alive yet not alive. I can fly yet always on the ground. I am delicate yet can lift tonnes. What am I?

Question: Oh how you love me: to some I'm a must. But to get what you need, you grind me to dust. I am dark and bitter, and when I'm white I lack meat. In winter you drink me, and in spring I'm used in a feast. I am a tree of summer and in autumn I'm a gift on an eve, while all year round I'm quite the reprieve. What am I?

Question: What is white outside and yellow inside?

Question: What is it that can get served but can't get eaten?