Thanks. Still not clear - apologies for being dense as the big US airlines don't do stopovers anymore. For example, I can't fly DCA-DEN (stopover)-LAX on UA. UA would consider this as separate tickets, but all airports UA flies without backtracking.

If I look at OTP-IST-CMB-MLE-IST-OTP, it doesn't exist on TK. Is the only stopover really possible at IST as I don't see any stopover options between OTP and IST for example.