I looked into the lightning code. The problem seems to be caused by the lighting using per-vertex lighting instead of per-pixel (so the entire polygon gets the exact same lighting), which was the old "basic" lighting model... and I can't find the function to use advanced lighting in the GMS2 manual... so it might've been deprecated in GMS2, so everything uses the bad lighting model now :<
Not sure about the "floor sticking" you mention... there is floor sticking I'm aware of (go through the door to dungeon_test2 and turn right, and then exit through the archway onto the stone void), but that's caused because you end up in the void outside the level and the collision checking is simplified (no slope checks - and floors have a height of 1 so their top ends up at z = 1 while the void is at z = 0). When I test play the first room, the transition between the small hedge maze and the indoors area works flawlessly.