Building question

Stalingrad book page 163:

BUILDINGS
See the Bolt Action rulebook for rules on buildings (pages 120-127). As mentioned in that rulebook, any building that is more than 8″ x 8″ in size should be regarded as two (or more) buildings for game purposes. If you’re lucky enough to have buildings models with interior details, it can work well to treat each room, hallway, and staircase as a separate ‘building’ in the case of a city fight.

BUILDINGS WITH MULTIPLE FLOORS / SECTIONS
In the Bolt Action rulebook, buildings which suffer 10 or more hits from HE are destroyed completely and turned into rubble (HE Weapons Against Buildings, page 124). These rules were largely envisioned to be applied to small buildings, such as single-family residences. However, Stalingrad and many other cities were filled with larger structures, such as factories, offices, and apartments, which could not expect to be destroyed by a single fusillade. Instead, treat each floor and distinct section as a separate building.

So the building rules apply to each section, and they can only hold 1 unit.

They should be treated as in separate buildings, so they get hard cover. You imagine the units are hiding behind furniture, cupboards etc.  You can also agree with your opponent that such cover are soft cover if you want.

All models that can draw line of sight to the target unit can fire. So as long as they can see each other, all models should be able to fire. Of course they should not be allowed to shoot through a wall, or between floors, unless there is some sort of opening, like a door or staircase.

In the case of a large room (like a big factory) divided into sections, all adjacent units should be able to shoot at each other as there are no internal walls.