The correct option is No, once a gist is public it cannot be turned into a secret gist.

GitHub sets gist visibility when you create it and a public gist cannot be converted back to secret later. If you want to hide the content you must delete the public gist and recreate it as a secret gist. This rule applies to all account types and it is a platform limitation rather than a permission issue.

Yes, GitHub administrators can perform the change is incorrect because neither GitHub staff nor organization administrators can change the visibility of an existing public gist. Visibility is fixed once the gist is published.

No, changing a public gist to secret requires a paid plan is incorrect because paid plans do not change this behavior. The limitation is the same on GitHub Free and on paid plans.

Yes, but only the gist owner can make it secret is incorrect because even the owner cannot change a public gist to secret after creation.

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