Well, this line returns the first 20 digits of your 24-digit serial number:
But the last 4 numbers (which I believe are some sort of a checksum) are
missing. Not sure how to get hold of those if you're not able to log on
to your Adobe account.
InDesign Server is a (VERY expensive) automation tool without a user interface. Are you sure that's what you are using? I don't know about ID server, but other registered Adobe products can be found in the user account of the Adobe ID that was used to register them, and serial numbers will be listed.
Yes, I'm certain this is what we're using. It's for the backend of a system and is used to generate pdf proofs and hi-res pdf compositions as part of a campaign managemeent system workflow. Unfortunately whomever originally purchased the software did so on their Adobe account so I no longer have access to it.