Thanks for your precious feedbacks!
Actually, it doesn't matter to block buildings with other buildings. So there must be other reasons that your buildings didn't work.
Number of pillars' supporting is just for test currently, maybe more types of pillars will be added into game in later versions.
As we posted in FAQ:
Q: How to hide other floors when I just want to interact things on specific floor?
A: Press F10 to switch floor view mode.
There are four modes:
- Show all floors
- Show current floor only
- Show higher floors(including current floor)
- Show lower floors(including current floor).
Right Click a blueprint waiting to be built to cancel it.