Here are the answers:
1) Define a tab type in “Product Tabs” menu, set “Use for all products” checkbox. If your return policy are the same for all of your product, then you can set the content of it in “Default Content” field of the tab type (and you can leave the tab content field empty on the individual product editor pages)
2) Define another tab type in “Product Tabs” menu, CLEAR “Use for all products” checkbox. You can choose if you set a Default content in the “Product Tabs” menu, or you set different content for every product on the product edit pages.
3) Create a tab type for it, Default content field of this tab type must be empty, and enter content for this tab only for the specific products (e.g. for product 123). Then this tab will not be displayed in case of other product (just for product 123). Please check if “Hide empty tabs” checkbox is set on the settings page.
You can set a general name for this tab (e.g Special Tab), and you can override this name individually for each product (if you use it for more products), if you enter a custom tab name into Your Tab Custom Title field on the product editor page (e.g. Special Tab Custom Title field).
If you have more questions, do not hesitate to contact us.