Impossible to answer without a serial number and detailed description.
Not in the open market
Fabrique Nationale (the name of the company) arms of war, Herstal, Belguim (place of manufacture. Brownings patent filed.
Depends on your pocketbook.
100-1000+ depending on specifics
This is an Auto-5 Shotgun
Yes, but not easy to find.
100-1000 depending on the specifics
Impossible to tell from just the serial number.
It stand for "national plant of war weapons herstal Belgium" Fabrique National is simply "National Plant" and it is common to call the Company "FN".
Basically impossible to value with just the serial number.