-vs- /proto sharing links

“View only prototype” doesn’t exist as an option for me.
Anyone with half a brain cell can change the url and see the full file, instead of just the prototype that I tried to share.

How do I get a prototype link that is view only, and sandboxed to the linked prototype only? *without just making a separate file

Please see the table at the link below to find out for which tariff plans there is a “can view prototype only” access setting: