Very poor description to base a value on. Broad range 300-800 USD.
Yes
You will have to call Colt with the serial number.
500-800 depending on what "very good" turns out to be.
No way to answer without the entire serial number. You can call Colt and they will tell you.
The Colt AR-15 is a sporter rifle
100-1000 usd
@ 40 inches.
Contact Colt, on line aucitons.
600-1200
Proofhouse.com has Colt sn data. If not there, call Colt and they will tell you.
To determine the age of a Colt AR-15 A2 HBAR Sporter with the serial number SP221219, you would typically need to consult Colt's production records or a firearms expert. However, Colt generally produced the Sporter model in the late 1980s to early 1990s. Based on the serial number, it's likely that this particular rifle was manufactured in the late 1980s.
Blue Book of Gun Values