DavidJames's post in Can't generate stairwell was marked as the answer
I'm not sure if this is what you're trying to achieve, but take a look at the attachment (I've also made some adjustments for clarity)
Also, it seems the reason you're stairwell wasn't generating was because you had an invisible wall near the top of the stairs for some reason(?). Delete that and the railings and try rebuilding.
Barn Copy - R1.plan
DavidJames's post in Ceiling and Wall Question was marked as the answer
Outline the walls above with invisible walls. This will create a room within the kitchen. Open up the room spec dbx for that newly created room and then drop down the ceiling height. Once the ceiling height is corrected, you can delete those invisible walls. See below:
DavidJames's post in Need Help With Simple Floor Heights - Again.... was marked as the answer
Floor heights have always been a headache for me.
However, I think in your case, the solution is simple. If you go down to your foundation level, you'll notice that your foundation is just one big room. So when you adjust the floor heights, it's adjusting everything.
If you outline the garage walls with the foundation below, this should solve your problem. Going forward, I think if you assign the room definition before you build your foundation, or have autobuild on, it'll automatically add those walls for you.