Imperial
Can hostile armies occupy every factory of a nation, or destroy its last unoccupied factory?
The rulebook bars hostile entry to a nation's only unoccupied factory and makes that factory indestructible.
No to both. Hostile armies may not enter a nation's last factory that is not occupied, so at least one factory always stays free, and that factory cannot be destroyed. The same protection covers the one unoccupied factory even when the nation has others that are occupied.