The Browning wwebsite, under customer service, has serial number ranges for different firearms. Yu should find yours there. VERY nice rifles, great caliber.
That Serail number dates the BAR to 1986.
700-1000
A gunsmith can help you.
You did not provide the sn, so the question can't be answered.
Check the receiver carefully.
Best to ask a gunsmith for help.
Contact Browning Customer Service, and request an owner's manual for your rifle. You WILL need the pictures in it.
What do you want to know?
500 USD
100-1000+ depending on specifics
50-500 USD or more
100-400 USD depending on condition.