To end up with this story, the plane I have taken was indeed a 767 300 with live TV.
...And clearly the first class seat do not even match a premium economy pitch.
I still wonder why some marketers called a product "first class" when it is far below any biz. Anyway, next time I will try to pay more attention and pick up the NW 747 flight instead.
Finally, I also politely declined the sandwich plate that came out during the night.