Sorry for taking so long to answer, but work and holidays got in the way! 🙂
Re. your questions:
C&S was always very light on detailing an actual world, they did have an “official” campaign published but was quite undetailed. Newer versions also have a campaign, but it’s quite generic. The older versions (1st and 2nd ed.) assumed you would be playing in a version of medieval Europe and that was that. A default period of 12th-13th century seemed to be the preferred one, but not too much so.
Lions & Dragon assumes a version of the 15th century Great Britain, with some fantasy elements thrown in, it’s not the Catholic Church but a kind of “Church of the Sun” a monotheistic religion similar in many aspects to the Church etc… I know they have a sourcebook on this fantasy Europe, but never read it, and probably won’t, I bought it (and many of the short supplements) for ideas on more “authentic but fun” magic rules.
I started playing D&D in late 81, and I think I played my first session of C&S in 85!