You cannot edit the .osu while ranked, but I think anything else can accepted. I'm not sure of what you need to do for that tho, I just know it was done before. However the past is the past, is it still a thing of today, idk.
You have to understand that once a map is ranked, score and pp can be gained, leaderboard exist, so changing the .osu will result in score and pp changes which mess up the leaderboard.