IIRC all domestic AF (and also AZ) are coach only, although I think you would get lounge access at CDG (and NCE if this is a RT). (That's what happened to me with an AirEuropa flight, where they even sold a separate ticket as business class despite not having business class seats (including no Eurobusiness class) on the aircraft.) Upon arrival at CDG, you should be able to use the Acces No. 1 (SkyPriority) immigration lines and other SkyPriority lines, but the same would derive from the D1 TATL segment. Once you clear immigration, it will be easier to use the special lines if your CDG-NCE boarding pass says SkyPriority.

In fact, having a same day D1 flight gives you (business class, not IFC) lounge privileges at any SkyTeam partner operated lounge along your route, so showing your TATL boarding pass might be the easier way to enter.

However, DL operates a nonstop JFK-NCE flight, IIRC on a daily but seasonal basis. It's often either full or expensive, but did you consider that flight? You might be able to get DL (assuming that you purchased the ticket directly from DL) to switch you without paying a change fee, although of course you should pay any fare difference.