1. i think it's more or less like that hand Aimi lost is apparently what has been guiding Flare(Megumi? ch21, after flare leaves the room ) and senpai through the place
2. the pictures shown on page ch 21 and current chapter somewhat resembles each other
no nevermind i was thinking of something else but i remember someone drawing the art in one of the earlier chapters
3. the medical centre mentioned never existed because it was not built yet considering that Flare was at least 10 years older from this chapter's timeline, however since the alien invasion failed in the past this may bring a different outcome or repeat itself
4. yikes