Tabs that matched Conditions will be shown on the product page. It also depends on the other fields like Status, Website, Customer Group, From-To, Discard subsequent tab.
If the product tab is not showing on the frontend after add or edit, then do reindex by run the below CLI command php bin/magento indexer:reindex product_tabs_rule
Yes, all selected items will be listed out on the frontend product view page. The customer can choose as many items as they want by selecting multiple checkboxes.
Yes, set the Enable for Product View and Enable for List View fields accordingly under the Permissions tab. Reference guide: https://magediary.com/docs/product-inquiry-support.html#permissions