I am interested to know how much has the language changed over the millennia. Is the relationship something like between Latin and Italian, maybe (I suspect) even further?

A hypothetical (or maybe not) situation when a speaker of Old Egyptian and one of Coptic try to speak to one another in their respective languages, without interdisciplinary training.

Would these two languages classify within the same family, if we ignore the genealogical connection?

Also, would be interesting to get answers to the same questions, but regarding all the languages of the Egyptian genealogy: Archaic <> Old <> Middle <> Late <> Demotic <> Coptic.