Depends on the understanding of a person. If they can understand the working of Bitcoin at the age of 14 then they may invest whatever pocket money they have.
Right. And Of course there are limitations for children who still don't understand finances and of course there are limits for older people who have started to experience senility frequently. So that teaching about bitcoin can only be done to people who understand finance and are also able to learn about technology and how to use the internet and the like. So yeah it all depends on the particular situation. In fact, we also have to limit ourselves not to teach people who are not interested in learning it.