I have a few questions, if I were to order Brutal Legend and New Super Mario Bros. now, when Brutal Legend came out would I be able to edit my payment method to apply the $10 credit towards Super Mario Bros.? Or would it happen automatically by chance since they don't charge you until a game ships?

Also, if I have multiple promotional credits, are they stackable or only one per order? Say I had three $10 credits from different games, could I apply all of those to a single game, or would I have to use them on three separate ones?