Depends on what is the most dirty. If you have used it near dust recently, be sure to remove the firing assembly and firing pin and clean those first, because they are generally the cause of jams.
yes
You will have to call Colt to find out.
Go to web site listed below and scroll down to Colt MKIV Series 80 & 90 It will provide you with the manual in pdf form.http://stevespages.com/page7b.htm
How can I find out what year Colt Combat Commander Mark 4 Series 80 was made?
Call Colt.
Proofhouse.com has Colt sn data
You will have to call Colt to find out.
You will have to call Colt to find out.
Experience and books
Follow the instructions in the owner's manual. If you don't have one, call Colt and they will send you one.
You will need to call Colt to find out.
To new for sn's to be published. You have to call Colt.