Spoilers.
Chapter V: Meakashi [Eye-opening]
Q: What's up with the title to this chapter? I've seen it translated as 'Eye-opener' and as 'Detective'.
A: "Meakashi" literally means "eye-opening." However, apparently in the Meiji-era, police detectives were referred to as "meakashi," so some groups translated it that way. They both fit in my opinion, Shion spends much of this chapter acting like a detective, and it is rather eye-opening for being the first Answer arc.
Q: Why are some of the earlier events different in this chapter compared to Watanagashi? For example, the delinquents confronting Shion instead of Keiichi, and Mion and Shion getting into a fight with everyone there when Keiichi finally meets them both at the same time?
A: This is to reinforce one of the 'laws' of Higurashi. In Higurashi, different chapters that have similar events occurring occur because a person has a strong wish for it to be true. For example, in every chapter, Tomitake dies and Takano disappears. Takano has a strong will to accomplish her revenge, but it cannot be done unless Tomitake dies and Takano disappears. In contrast, Sonozaki Mion has a high desire to play club games with everyone. But she doesn't particularly care if they play cards, a board game, clue, or something else. Thus, the small events in Watanagashi and Meakashi are different, even if the large events generally are the same.
Q: If the Sonozakis really AREN'T such a bad family, then why do they force Shion to tear her fingernails out?
A: There's a TIP in the original game that all Sonozaki matriarchs get their fingernails pulled for some reason at one point or another. Sonozaki Akane, Shion and Mion's mother, reveals that she herself was forced to do it, and so was Oryouu Sonozaki. Apparently, the fingernail pulling is some sort of Yakuza rite-of-passage.
Q: Why does Shion beat the crap out of Rika?
A: Because she's crazy and she believes Rika helped 'disappear' Satoshi. XD; It's not too deep a reason.
Q: So Rika 'hearing Oyashiro-sama's voice' is actually Hanyuu?
A: Yep.
Q: Why did Rika try to pepper-spray and then syringe Shion?
A: Because Rika had already lived through at least one variation of this world, Watanagashi-hen. Therefore, she knew Shion was going insane, and tried to defend herself.
Q: Did the syringe make Rika kill herself?
A: No, the fear of knowing Shion would torture her to death if she didn't kill herself right there made Rika kill herself. The syringe contained the 'antidote' to Hinamizawa syndrome. Rika is the Queen carrier, but supposedly her level is very low. The syringe wouldn't do more to her than just the pain of being stuck with a needle, roughly.
Q: If Rika commits suicide here, why doesn't Rika commit suicide in any other world? Like when the Yamainu go to 'retrieve' her?
A: Keep in mind, when Rika is killed by the Yamainu, she doesn't know who's doing it. This is influenced partly because the Yamainu drug her, so Rika's death at the hands of Takano is actually pretty painless. This is why it remains a mystery to Rika and Hanyuu for so long, Rika gets put to sleep before it happens and Hanyuu is too much of a coward to watch.
Q: Is there anything else that should be mentioned about the scene Rika kills herself?
A: Yes. In the games, as Rika stabs herself, she screams out: "HANYUU!" Presumably, because Hanyuu would also be able to feel the pain...
Q: Satoko seems pretty mentally stable in this chapter. Why is she okay here compared to Tatarigoroshi-hen?
A: Because in this chapter, her uncle doesn't return and therefore she is still receiving injections of the Hinamizawa syndrome antidote.
Q: Why does Kimiyoshi (the old village leader) agree with Shion that the Sonozakis are likely the ones responsible for Satoshi's death?
A: Kimiyoshi is an old man and Shion has him in a torture device. He'd tell her anything to get her to stop torturing him for a minute. In the end, it seems, Kimiyoshi himself had no idea the Sonozakis were 'controlling' Hinamizawa through a bluff.
Q: Does Shion really have a conversation with Satoshi's ghost at the Sonozaki death well?
A: No, Shion was batshit crazy and imagined the entire thing. If Satoshi really was down there, the police would've found him with the other dead bodies after the incident.
Q: Does this chapter REALLY only occur because Keiichi didn't give Mion the doll?
A: Apparently. In the PS2 games, there is an alternate choice. Keiichi can choose to try to give the doll to Mion (she refuses it,) and then follow up by accepting Mion's tea at the Watanagashi festival and realizing before seeing them both at once that Shion isn't Mion.
If you select those choices, you have the option of continuing the game like this when Keiichi is strapped in and about to be tortured:
Keiichi: "There's no way you're Sonozaki Mion. :|"
Shion: "Well, then who am I, I wonder...?"
Keiichi: "...SHION! You're Shion!"
However, this results in a bad end as Shion gives Keiichi the Watanagashi-torture right there.
Q: Is there anything else that got edited out of the anime that was in the original games?
A: Yes. There's a revelation that the Sonozaki twins have actually been switching places since they were little girls. So much so, that the younger girl who was born as Shion was in the "Mion" role when "Mion" became tattooed as the new Yakuza heir. They tattooed the wrong twin when they were about eight-ten. So Mion is really 'Shion' and Shion is really 'Mion'. When the twins are alone, they go back to calling themselves by their original names. After Shion has Mion locked up, she starts accusing Mion of intentionally stealing Shion's birthright from her. Another reason why Mion put up so little resistance to Shion.