1. Sure, this URL should work because the default theme uses the same URL for the “Submit Listing” button, please make sure that you copied it without any changes. If there’s a redirect to a strange URL please make sure that there’re no posts or pages with the “submit-listing” slug, they may conflict with the listing submission URL added by HivePress.
2. Please mark products as “virtual” and “downloadable”, then orders should be marked as completed automatically and user will be redirected back to the listing submission page (this redirect occurs if user visits the “Thanks for your order…” page and order is marked as processing or completed).