This game isn't a port. It has new levels (96 in total), enemy (Buried Guy) and objects (rocks), and its gameplay is a little different (a portal must be taken to complete a level). It has better graphics and music than most of other console 2D versions except the SNES version which was just a remake of the Lode Runner for NES.
IIRC, there is a Buried Guy hidden in a certain brick block every level. He carries a bonus teddy bear and to get it you have to trap him in a hole. He won't reborn if you kill him in the current level. Otherwise he is just a different-looking baddy as the others. You don't either need to reveal, trap or kill him, or get his teddy bear to complete the level.
Rocks are acting like plain boxes in other games. They can be pushed, used as platforms and baddy crushers, or buried to vanish permanently. Baddies cannot move Rocks.
I've made a short
test run using the (J) ROM since no (U) or (E) ROMs are available. I completed 3 levels in Small World, getting all teddy bears dropped by the hidden Buried Guy. I'm not sure if collecting them is a good idea since in some levels collecting them takes considerable time.
EDIT: About the Buried Guy and Rock objects.
EDIT 2:
Level 3 redone using a better solution.
However...
Here's a run with 3 levels done without collecting any teddy bears. I'm tending not to collect teddy bears now since I found the Buried Guy can be spawned in one of two places in most levels, and you see how dealing with him prolongs the run....