Yeah it's a bit strange to ask, but is GBStudio allowed for the game engine/making tool?
I think you can use it but you'll need to limit the screen area of everything that the player can see to only 84x48 pixels which is less than a quarter of the GB screen size of 160x144. (If you doubled that, you'll get 168x96 which has higher width than GB size and that will probably disqualify you.) If you can manage to make it work, I would like to see that!