Is it OK for me to ask a list of configuration releases that has been done by the vendor in the UAT and Pre-Prod environments? Please validate
It would depend upon what as been agreed and who is responsible for the configuration - if this is a task you have given to the partner I would expect them to be able to track them as to what was set - however I would not expect a document “explaining” why they were set at a field by field level unless this was contractually agreed (it would be a long document to create). Reasonable to ask, the answer however depends upon the contract and methodology.