Since all countries don't have the same study you presented I could go down a deep rabit hole looking for church going but irreligious populations especially in countries where it is taboo to be irreligious and thus the stats can't be collected. Interesting though.
I've always thought of "Christian" as a faith rather than a religion. "Roman Catholic", "Lutheran", or "Baptist" (among many) would be a religion. I've looked and there is no absolutely correct answer. LOL, but I sure didn't do well on your cool quiz because of that!
https://en.wikipedia.org/wiki/Religion_in_Sweden
Since all countries don't have the same study you presented I could go down a deep rabit hole looking for church going but irreligious populations especially in countries where it is taboo to be irreligious and thus the stats can't be collected. Interesting though.
https://en.wikipedia.org/wiki/Freedom_of_religion_in_North_Korea
I'll look into it further. Thanks.