I think there's no specific answer for these questions. Individual people differ so greatly....in age, maturity growth, life experience as well as life circumstances. A young child can own an "exotic" if his/her parents are also willing and able to be a part of the process and supervise. And some grown people I know should never own an animal of any sort, regardless of how "exotic" or common it might be.
Is maturity directly linked to age? I would just say there is a very strong correlation between the two. It might be more accurate to say that there is a direct link between maturity and life experiences. Some children experience more life in their few years than many older people. And some people seem to never learn and grow, no matter how much life they go through. But, in general, most of us grow and learn and grow some more as we age. I'm WAY more mature now than I was when I was 30....and was more mature at 30 than I was at 20.