RE: How do we change the serial number in the serial number list for an item in inventory
I think the Item reclassification journal can help you with a lot of these issues
You can read more about how that can be used here:
learn.microsoft.com/.../inventory-how-work-item-tracking
The journal will let you change serial number on inventory you already have.
When it comes to updating older transactions that can be a bit more tricky if they are already soled.
To make sure that is done in a way that do not create inconsistency in your data I would recommend that you discuss with your partner how that can be done.
And please circle back if you have any more detailed question around what the reclassification journal can do and how it should be used.