Explanation:

File1
Location: SharePoint Online.
Created: Dec 28, 2015.
As of Jan 1, 2025 # File is 9+ years old.
If retention is (example: 7 years), then the retention period has expired, and the file will be deleted once the policy is turned on.
# Answer: Yes
File2
Location: OneDrive.
Created: Jan 2, 2015.
As of Jan 1, 2025 # File is 10 years old.
Retention period (7 years, for example) has expired # File will be deleted once the policy is turned on.
# Answer: Yes
File3
Location: Exchange Online public folder.
Created: May 1, 2010.
As of Jan 1, 2025 # File is 15 years old.
But Exchange public folders are not supported locations for Microsoft 365 retention policies.
Therefore, policy does not apply, and file will not be deleted.
# Answer: No