Well, I'm not sure how the levels work in Canada so I'll let someone else cover that part as far as if it's realistic in four years. But I do want to say 14 is certainly not too late to start, and to compete. What the requirements are really depends on the gym, some bigger ones you have to be invited onto the team, others (like my old gym when I was in high school) allowed everyone who was working on the appropriate levels to compete and train with the team.
There are a lot of factors in how long it will take you to learn skills and advance through the levels, some people pick the skills up practically overnight, others take years. You'd be looking at a lot of hours in the gym, and many more outside the gym stretching and conditioning to get into good enough physical shape to perform the skills. It also can get rather pricey, so make sure your parents are willing to financially support your goal.
~Katy