It means that you can combine the all items code with the MOD shop code ONLY. If you try to use it by itself, nothing will happen, or it could crash your game. The MOD shop is where you can buy these items. Combine it with the "Free MOD shop" code.
On Em, you can trade with FR and LG, but only the pokes that are included in the Hoenn dex. You have to get the National Dex, after you defeat the E4, to trade from the Kanto and Johto regions.
Cyote...