I don't understand this question. Once you become physically 19 or 20, you become neutral and won't age anymore. I definately don't believe in the eternal part. You don't have to limit your beliefs. Sky is the limit.
Humans can accomplish anything because they are so creative.
That's all in your mind. The reality is far more flexible than that. Nobody can tell what is possible and what is not possible before a test is conducted and results being shown. So my friend, do not put a limit on your belief system. It's not doing good for you.