I have sent some messages to some unknown profiles on Facebook messenger months ago. Now, I don't want them to see my messages anymore. What can I do? How can I make my messages disable to read for them? I want to hide my messages in their messenger conversation.
From Facebook Help Center:
No, sent messages can't be unsent or removed from the person's inbox. Depending on the persons's notification settings, they may also receive your message as an email notification.
Keep in mind that deleting a conversation from your inbox won't delete it from your friend's inbox. It isn't possible to delete sent or received messages from a friend's inbox.
Here is a workaround you can try. Report that sent message as Spam, and then delete it from your inbox. Now deactivate (don't delete) your profile for few hours and then reactivate. Probably those persons will not be able to see your message.