Originally Posted by
Fabo.sk
I've been a guest in the FCL myself earlier this year, with another forum member having arrived in F, us later departing both on the same flight - me in Y, his in C.
So it seems that the no guest on arrival rule might apply, but only if you don't have a further out connection (which OP does)
This is also not quite correct. I had arrived from DXB in the morning in F and continued to ARN to then immediatly return to ZRH on SK. Once that was done, I went to have dinner in the F lounge 12 hours after I originally arrived and I asked if I could guest a friend, to which both supervisors told me that that would be no problem as long as the guest has a valid arrival or departing *A boarding pass. It doesn't even have to be the same flight as you arrived on.
So even as pure arriving F pax you should be able to use the F lounge as arrival lounge with a guest.