Chapter 5, she only needs two points though. Two points generates two circles, which have two intersections. Since one of them will be outside the area she can be active in, the other must be where her soulgem is.
Why would they hold Kyouko's soul gem during the race?
It's a temperature endurance test. The competitors are bundled up and under a kotatsu, during summer. Since magical girls' bodies aren't their actual body, etc etc, if they kept her soul gem at room temperature, then Kyouko would also feel she's at room temperature the entire time. But Sayaka being lazy puts her soul gem on a left-under-the-summer-sun metal barrel which leads to Kyouko overheating and losing.
Ah, it was worth the wait! This series is honestly amazing, kinda sad some of my other favorite mangakas aren't really making Madoka Doujinshis anymore, or maybe they are, but the newer ones are still being translated.
In Ch. 2, Summer Stories Series 1, Homura is retelling part of Cixin Liu's novel "Three Body Problem." It's really good!
What's the distinctive part that marks it as "Three Body Problem", and not a generic UFO/smart aliens story?
Ah, I guess I was reading the second and third panels as describing one of the suns on Trisolaris, but I guess it could have been a generic UFO.. I feel like since everyone else is confused, though, maybe Homura was making a reference no one understood?