Explanation:

Box 1: Yes
You can use sensitivity labels to provide protection settings that include encryption of emails and documents to prevent unauthorized people from accessing this data.
Box 2: Yes
You can use sensitivity labels to mark the content when you use Office apps, by adding watermarks, headers, or footers to documents that have the label applied.
Box 3: NO
https://docs.microsoft.com/en-us/information-protection/deploy-use/configure-policy-markings

Reference:
https://docs.microsoft.com/en-us/security/zero-trust/

Reference:
https://docs.microsoft.com/en-us/azure/active-directory/external-identities/what-is-b2b