How long have he and Basil been enemies?
a. Probably since adulthood, if not farther back. At least one of Eve Titus’ stories (I’ll get back to you when I have more info on this) suggests that Basil and Ratigan’s personal war went back to their college days. What exactly inspired their mutual animosity is as much a mystery as the hostility between their human counterparts. It may even be possible that it goes back to childhood, at least when they were in their teens (also, refer to question 6 above).