Reddit user saras112 posted the following screen shot on Android mobile phone, showing the option to delete messages on Facebook Messenger for senders or all. As it is now, users can delete messages from the session, but deleted messages are not deleted from the recipient's application. You can delete any message sent to anyone, but coping will still see it in the chronological order of the conversation.
What you can't do now is delete a message for everyone, whether it's a conversation between two people or groups. The word "unsend" is not used in the screenshot above. There are no time limit instructions in the above tips. Similarly, according to previous Facebook updates, the cancellation function only applies to messages sent during a 10-minute window.
Facebook has introduced a similar feature for WhatsApp, in which users have an hour to retrieve messages already sent, and it is not clear why there is such a large time lag between the two platforms.