A member of a group chat in FB messenger has deactivated his profile for a while. Will he be able to see the messages in the chat exchanged while his profile was inactive if I delete those messages?
No, once a person deactivates their profile he will not able to see any activity of anyone from their profile and no one can send them messages. So a group message is not delivered to that person. If you do not delete that message, (s)he will not be able to see those messages. Even after the person restores his/her profile will not be able to see the messages.