How do you get 999 master balls in a non-cheating way

beat the league, catch at least 200 Pokemon, have at least 5 legendarys, and have 800 battles with people. then you go to any Pokemon center and talk to the people on top. the will say: hello! welcome and your professor said that you did a good job on your adventure! he told me to give you this: obtained 999 master balls!