There is no copyright restriction, but it is best not to use it for commercial purposes, especially the Forbidden City, which is quite special.

Ordinary should be fine. After all, there was no such thing as copyright at that time.

You use materials as models, so you shouldn't apply for a patent, right? You can only enjoy the copyright of this mode, and the copyright will be automatically generated when the work is completed.

Works of art that can be reproduced, painted, photographed, recorded and displayed in outdoor public places.