the Bolo. Residential units are measured in "bolos."
Residential building codes vary substantially from municipality to municipality and should be checked locally, but at minimum a hallway width should be no less than 36 inches.
It may be different for your area. In my area the garage ceilings and walls which join living area have to be 5/8". All others areas 1/2" is fine.
6.5 inches
You may get by the code, your lender will not like to hold paper on a floorplan which does not resell...
No