PDF A3 - B2B model

Clearance and Reporting
1
  1. How do we validate the PDF Invoice copy is belonging to PDF/A3 because all the PDF files are having .pdf as extension?
  2. If we see an XML attached to the PDF invoice, then can we consider that it belongs to PDF A/3 family ?
  3. If we are sending regular PDF Invoice format and Inbound response received from ZATCA as two separate attachments in one email to our customers, does this qualify as EInvoice compliant ?
2

please check the published international standards for this file type.