Restrict duplicate request to be created on the basis of catalog variable

[shrutikasin]

What is the recommended ServiceNow approach to prevent duplicate catalog item submissions when the duplicate check depends on a catalog variable (qr_value)?

Specifically:

1. How can I stop the submission before both REQ and RITM are created?
2. Is checking sc_item_option_mtom the correct approach for catalog variable duplicate validation?
3. Is there a better architectural solution than a BR on sc_req_item?
4. Has anyone implemented duplicate prevention for catalog variables in Service Portal successfully?

Any guidance, examples, or best practices would be greatly appreciated.

Thanks in advance!