Good Riddles

Question: what is ready when you add a letter inside?

Question: I'm not dead i'm not alive, i'm not underground i'm high up in the sky, people speak of me but never saw me. Who am i?

Question: i have a house but it doesnt have a door?

Question: What is tall and have 4 legs

Question: I'm the one that gives you information, I'm the one that lets you have the ability to control yourself, I'm the one that stores all memories and without me you'll be dead in a instant. What am I?