Auto overwriting old records with same unique element?

In Unifier we have Business Process named Tender Tracker, user wants to reupload a same set of data through .CSV file for any form of update in any tender.

Question 1- The BP will be having a unique element called tag number. While reuploading a record with a tag number that is already present the system should throw an alarm or option whether user would like to overwrite or make a new copy of the present tag number record.

Question 2- A different BP named Procurement, having BP picker of Tender Tracker picks record and auto populates the Tag number, the records in this BP will also be created in bulk through .CSV file and will be reuploaded for every update for each tags. If the tag mentioned in a record is not present in Tender Tracker then the system should through a message that the tag is not present in Tender Tracker.