1) We have a few demos that built using different multivendor plugins https://prnt.sc/19ru1k9 Go to https://xstore.8theme.com/ and click Multi-vendor menu item.
2) It depends on the multivendor plugin you choose. It would better to contact plugin author to clarify this question. Our theme does not have such option, it’s a plugin area.
3) Yes.
4) It depends on the plugin you plan to use. As a rule multivendor plugins display the vendor name on the single product page.
