1. Alternate2 on top of overworld
2. Pillar to the top of overworld
3. You can place a block on the pillar and it will be placed on Y 0 in alternate2

I tested and the block placing works normally as you described. What do you mean "pillar"?

@qouteall if there is a block at y level 255 and you try to place a block on top, it says the build limit is 256... unless I'm wrong and you actually implemented this

Closed because already implemented