Hi Englishsz,
Here is my two cents:
There are 4 cities but only 3 initial homes built as models to be shown. The statement was not clear and created disagreement.
A [demo] is equivalent to a [model] or [sample display]. created for the demonstration is a very confusing phrase. Perhaps [built to be shown as models] may be an alternative.
[Staging] is the wrong choice of word here. Be careful how you use [staging]. Used wrong, it create a skewed picture. Here is a couple of scenarios where [staging] can be used.
The area where people set up tents and tables for water supplies, medical facility and course controls of a 10k run is the [staging area], sometimes is called [command post].
As the U.S. Air Force’s C-130 carrying the earthquake rescue supplies and equipment landed on the tarmac, the Marines on the ground quickly unloaded the cargo and set up a staging area to distribute the desperately needed resources.
Staging a scene – is to theatrically played out a scene for the purpose of deception.
Staging a home – sounds murky.