Yes, only after creating a cost sheet against this preliminary invoice, then on right-click action there is an option for converting original.
Yes, you can add quotation details to supplier invoice and cost sheet.
If we do not fill the Tax number while creating invoices, the same will be in disabled mode while making invoices against that particular supplier.
No, it will not be reflected in the finance summary.
No, It does not create automatically however you can fetch the quotation data while making invoices.
Yes, you can directly make a cost sheet by skipping supplier invoices.