Depends on who it is, you get back what you put into it. Me, I do at least something everyday to improve myself, if I don't have something I need I make it, I also watch fights over and over again on fighters who my style is similar to, I keep a notebook of thing I learn and ideas I have, along with combos I practice.
never if the pug does not have "it" physically. If he doesn't have it mentally possibly never too. Athletic talent has a way of going around technical skill.
10 years or 10000 hours, less if you have some transferable physical abilities/skills from other sports.