The 20A00 (OP2) comes in two 'flavors:' no flash update (discontinued) and flash update. Either 'flavor' comes in a -2 model (in enclosure), -8 (on structured plate), and -21 (board only). The 'no flash update 'flavor' comes addition in a -5 model (in commercial enclosure).
The latest PC Access Dealer documentation is contained within the Help files of the s/w. I have not ever seen a written document for PC Access Dealer.
I have never seen a 'blow by blow' single document of changes made for each version.
Version 3.17 is that last version supported by the no flash update 'flavor). Anything above 3.17 running (properly) means that it's an OPII flash update flavor.
Installation manuals include 20J00-2 (or -5, -8. -21) V2-04 May 2003 or V2-13 Jan 2006. Owners manuals include 20R00 (or -5, -8, -21) V2-11 Jan 2006 or V3-2 Aug. 2008. All of these are in PDF format. I'd be happy to happy to share provided an email address to attach to.