Headscratchers / Love Live! Sunshine!!

• How does the mysterious girl in Otonokizaka remembers µ's but Riko didn't?
  • Since they left no trace of themselves in the school, the answer is that it's probably for the same reason Chika knew of them but Riko didn't: Riko was never interested in school idols, she was focused on her piano career. It was less that she didn't remember them and more that she never cared for the subject of µ's and so never bothered to learn about them. That girl was likely a fan of µ's before getting into Otonokizaka, perhaps even went to that school exactly because of the group. Either that or she noticed that people inspired by µ's often stopped and stared at her school in awe, and took to herself the job of explaining that there's nothing of them left in there.
• Why is Dia's name pronounced as "Daiah"? Isn't her name Japanese to be pronounced as it's spelled?
  • Her name is spelled "Daiah" in Japanese, it's ダイヤ in katakana, which is read "Daiya". It's romanized as Dia because the idea is that both her and Ruby were named after precious gems: Dia is supposed to be like a short version of "Diamond".
• If Hanamaru's family runs a temple why was she sent to a catholic school like Uranohoshi?
  • In Japan, the prevalence of syncretism (de facto mixing of religions) means that people can be "born Shinto, married Christian, and die Buddhist" and often see no conflict whatsoever in it, nor consider themselves to have even "changed religions", much less converted. Since all forms of Christianity combined still comprise just 1% of the Japanese population, it's not like any Catholic school can afford to limit its student population to Catholics, either. There's plenty of real-life cases of Jewish and Protestant (including Mormon) parents sending their children to Catholic schools in the United States, too: after all, if it's the best private school available ...
• About the main photo: How did Hanamaru, Ruby and Yoshiko get second-year uniforms? (You know, the ones with red scarf)I understand it from Kanan, Mari and Dia who were second-years in the past and may still keep their red scarves, but Hanamaru, Ruby and Yoshiko have never been second years so how is this possible?
  • If you're talking about the Characters' page picture, that was the first picture released of the girls ever. It's really old, at the time they probably didn't have the intention of immediately revealing which girls were first, second or third years and so put them all with the same uniform.
• In episode 7 of the second season, the Aqours gang awaits the enrollment of new students after their terrific performance that made them pass the preliminaries, since they need 100 new students in order to save the school. The video of their performance is making waves on the Internet, so it would make sense to enter the chat room of the video site to engage with their fans, or (better yet) start a livestream in which they can personally ask their fans to enroll. But no. The girls do nothing, bitching and moaning about how not enough students are enrolling, and at one point Chika even suggests going to the train station to ask people for help. Really, Chika? Why would you go to the station when you have the means to potentially reach millions of people?
  • Because the issue is getting people to enroll into the school, and the people who they engage with online aren't guaranteed to live close enough to Uchiura to consider attending Uranohoshi. Unlike µ's, they live in a rural fishing town, not one of the most populated cities on the planet, which made things easier for µ's. The smaller population ultimately makes it harder for the Aqours girls to get people interested enough into attending Uranohoshi, unless they already live in the region. Thus, it's more practical to check out the train station for people who live nearby.