I was able to input the code. To get it to work in game however, takes some work. Turn the code off, then select the first starter. Once you receive it, turn the code on, and select the second one, turn it off. After you receive it, turn the code back on, and select the third. Once you select it, turn the code back off, and receive it. Gary will select the opposite of your last pokemon. Open your menu and you will have all 3 starters.