Rocks'n'Diamonds

When I was messing with a level that came with the emerald mine engine, I was replacing an emerald mine style exit with a steel emerald mine style exit, when I played the level, it says it's not in emerald mine.

That's because Emerald Mine has no steel exit natively. Any element not present in the original Emerald Mine games will be displayed with a ? if using the Emerald Mine engine.