Inquiry regarding required documents and eligibility for simplified tariff drawback

The transaction structure is A (Manufacturer) → B (Buyer) → C (Exporter). B and C are not involved in manufacturing and do not handle the transfer of raw materials; instead, B purchases the goods produced by A and sells them to C, who then exports them. All raw materials used during A's production process are of Korean origin. In this situation, I have a few questions: 1) When C applies for a drawback, are the required documents the Certificate of Small and Medium Enterprise (issued by the Minister of SMEs and Startups), the Processing Contract (containing all details of the processing entrustment), the processing tax invoice, the Raw Material Delivery Confirmation (or the Certificate of Basic Raw Material Delivery—I am also wondering if these two are the same document), and the Export Declaration? 2) Should the applicant for the drawback be listed as the Exporter on the Export Declaration? 3) If the manufacturer is listed as "Unknown" on the Export Declaration, will it cause any issues when the exporter, C, applies for the simplified drawback? 4) Can a Certificate of Basic Raw Material Delivery (기납증) be obtained even when the raw materials used in production are of Korean origin? 5) For a company like B, which purchases finished goods and sells them to C, is it correct for them to receive a Certificate of Basic Raw Material Delivery (기납증) rather than a Certificate of Raw Material Purchase (분증)?