No - because of the stopover. F check-in/lounge does not apply just because there are F sectors in the booking 'somewhere'.

You can use F check-in at Canada and the Flounge there if applicable to the station. After your stopover, for LHR-IST, you can use the Club check-in zone at T5 - again, at the South end, near the F check-in and South security. You can then use the Galleries Club lounge(s) assuming your are not AA EXP only Plat. On the way back IST-LHR-Canada you can use Club check-in at IST and the Terraces lounge, and then after re-clearing security once you've landed at LHR, can make your way to any of the T5 airside lounges for before the LHR-Canada leg, including the CCR (which is the best) but you could also try the Flounge if you wished.