https://github.com/ttocskcaj/ElementalCraft/tree/b4931beb400823e81610d2d3854271204be8de57
After getting the dimension working with 2 biomes, we made the decision to split out "Elemental Plane" into 4 dimensions anyway (one for each element). There's link to an older commit, but it was working with 2 biomes at that point.
Correct.
And this is why I have my registry code done up the way I have.
https://github.com/Draco18s/ReasonableRealism/blob/1.12.1/src/main/java/com/draco18s/hardlib/client/ClientEasyRegistry.java#L64-L71
I search for all valid states of the block (note that this method is not good for things like leaves which have states that don't appear in the inventory) and register an item model for each.