a4phoenix

Happy holidays everyone!
I want to share my recent experience with TK and ask your opinion on this matter.

So, what happened was:
- I was on my way to Europe for new year holiday with TK , route is XXX-IST-OSL//TXL-IST-XXX, all in one ticket
- My original plan was to have a long layover in Oslo, get out to the city, and take a D5 flight (separate ticket) in the evening to Paris, my main destination. (Flight to Oslo was cheaper than to Paris and I've never been to the city)
- I have a valid Schengen visa issued by Embassy of France
- in IST I was denied Boarding because the gate agent said "you won't be allowed to enter Schengen in Oslo"
- even after I showed him my D5 ticket, he wouldn't budge and the plane left without me
- he took me to TK "Care Point" to settle my issue there and left
- I explained my situation to the TK Care Point agent but after a few call to "visa office(?)" , all of the agents I interacted with said the gate agent was right because I need to first enter Schengen via France before going to other Schengen countries.
- I told them when I applied for my visa the requirement only stated that I need to apply Schengen visa in the Embassy of "country of my point of entry OR the country where I plan to stay the longest".
- the agents wouldn't budge and said "sorry, I'm not a visa expert but the visa office said that is the general visa requirement. Since this is the first time you use your Schengen visa, you wouldn't be allowed entry in Oslo or anywhere else outside France."
- I asked if there is any such written in Embassy page or IATA but they just said "sorry, you need to buy a new ticket."
- at the end I didn't want to spend too much of my holiday time arguing and just bought a separate ticket direct to Paris

So my questions now:
1. Am I wrong thinking that I could use my Schengen visa to enter any Schengen country? ( I was planning to spend most of my time in France)
2. Any recourse to recoup some of my losses ? (Lost time in Oslo, unused D5 ticket between OSL-CDG, new TK ticket between IST- CDG?

*Side note: 10 years ago I had a Schengen visa issued by German embassy, enter visa Copenhagen, spending most of my holiday in Germany, and left visa Switzerland. Has the rule changed since then?
*To me, this is not logical because that means I cannot use any of the Schengen airline for this holiday beside Air France or La Compagnie , due to other airlines itinerary's need of transit.

I'm not letting this experience ruin my vacation, but really want to hear a good explanation.
Thanks in advance!