I have heard you can get Arceus by going to Jubilife city and doing something without national dex to get Arceus Is that true

if you have an action replay....go to youtube, and try to find the video with all the codes and in his description box it says after you do the code, you can go to the museum in one of the first town and get ANY Pokemon at level 20......including arceus, lugia, and every other one.....