They aren't actually working yet. A temporary fix was done to allow for milking (i.e. you need to /maskscent), but the actual effect isn't implemented yet.
No, it has not. It is being worked on though
Yea, those condemned structures were essentially invisible--it's why some people still had the lots and/or vendors still applying to their overall count. I don't know how the removal is being handled.
The maintenance fix for commercial structures was indeed retroactive. They should have been charged maintenance all along, but a bug was preventing it. There were notes to that effect on the testing spreadsheet--but I'm not sure if it was stated anywhere else.
And in other locations too. They've always been there, just not active