20/20 vision is NOT a requirement of commercial airline pilots. If you make it far enough into the selection process you'll undergo some medical examinations, and although they test your vision, they are not testing for 20/20 vision...they also do tests with your corrective lenses on. 20/20 vision is a requirement of air force/fighter pilots - not commercial.
There is no "set" subjects to take at university....the CPP accepts candidates from a wide variety of backgrounds - in terms of flying experience and in terms of academic subjects.
Though rare, there have been instances where candidates were successful in the application process right out of high school.