Answer:
Never ahead, ever behind, yet flying swiftly past; for a child, I last forever; for an adult, I'm gone too fast. What am I?
I can be swallowed, but I can also swallow you. What am I?
I look at you, you look at me. I raise my right, you raise your left. What am I?
I start new then become old. Start clean but be one dirty. I usually start big then become little.
I'm a god a planet and a measurer of heat. Who am I?
Though not a plant, has leaves. Though not a beast, has spine. Though many wouldn't need this thing, It's more valuable than wine.