I am considering a flight with routing ORD > EWR > FRA > DBV. I know I can get there more directly than that but I want to meet up with friends in EWR on the way. My flight from ORD > EWR would be United First Class, EWR > FRA Polaris Business Class, and FRA > DBV is Economy on the partner Croatia airlines. There are no business seats available on the flights I found from FRA > DBV. This is all on the same ticket.

I know I am entitled to use the Polaris lounge at EWR. My question is, do I also get lounge access at ORD? And is it the regular or Polaris lounge? Also, in FRA, would I have lounge access there since my ongoing flight is in Economy?