A: No. There is a "Chaos" ending if you try to betray everyone, but it results in all heroines dying. The true ending is exclusively Rinne.
Consistently interact with Nemu whenever she isolates herself from the group. euphoria visual novel guide
To unlock a specific character's route, you must choose them repeatedly when given the option during the "Game" phase. The game tracks your "Points" with each girl invisibly. euphoria visual novel guide
Rinne’s narrative path shifts the focus toward the psychological breaking points of the captives. euphoria visual novel guide
You will reach a point where you believe you are in a simulation and are asked to trust a character resembling Kanae.
If you choose "但是..." or "でも…" at the critical decision, you will receive a Bad End (to collect CGs).