No, and yes. But mostly no.
As far as the episode itself is concerned, according to staff interviews the decision was taken to have the crew of the Demon-Class Voyager return specifically for that episode. It follows that none of the prior episodes were (intentionally) about the doppelganger crew
"Bryan Fuller came up with the idea, what if we followed the
adventures of those people that we left on the Demon planet?" - Joe Menosky - Cinefantastique, Vol. 31, No. 11, p. 49
"In terms of how it got started [...] we sort of liked the idea of
picking up the mimetic crew, and finding out whatever happened to
them," - Nick Sagan - Star Trek Magazine issue 114, p. 3
That being said, the door was left open slightly.
"We didn't want to answer a lot of questions, like, how long has that
ship been out there? Some of the episodes that we saw earlier in the
season, was it that crew? Or was it the real crew? It's kind of
intriguing to think about." Ken Biller - Cinefantastique, Vol. 31, No. 11, p. 50