For the IV code the last six lines corespond to each IV Hp, Atk, Def, Sp. A, Sp. D, Spe. and yes it changes them via marking.
The code is correct in regards to the 211F, the last byte on each line is all you need to worry about.
The nature mod code simply changes the pid so that the pokemon becomes that nature/gender (erasing shininess), and if I remember correctly the male codes make the pokemon female and vice versa, while you can use either on a genderless pokemon, if you want the pokemon to be shiny again use the shiny marking v2 code.