Pretty sure D&D requires a 4M card, not neccesarily a 4-in-1. Some games just require a 1M or 4M cart to play. Some even require a specific cart for that certain game.

edit: and since it's an import, the swap trick doesn't bypass the region protection. If you want to play a burned D&D in a US saturn, you will need a 4M compatable 4-in-1 (if i'm right about it needing 4M to begin with, which I'm pretty sure is the case). If you used a region bypass cart, you'd probably get nothing but a screen full of japanese with "4M" in it somewhere, telling you need the cart. And you cant change out carts while it's on (it's very risky, and doesn't generally work anyway).