For C8, you need to choose the rope instead of the apron at the end of the investigation phase at the beginning of C7! Then, at the failed section where you can get the ending 'trio run away' (you can check the Walkthrough for more information), and unlock a hidden bad ending!
As for the D7 achievement, I checked the code and found it was a bug! I forgot to add the code to unlock the achievement TT This isn't your fault, It should actually be obtained in the Mirror Twins section!!
Thank you fo being willing to spend time to collect all the achievements and letting me know about this bug!! but sorry for can't get all the achievements for now!!o(╥﹏╥)o I'll release a revised version in a few days!! ( As I think there might be more bugs that haven't been reported... and the data transfer fee for uploading once is a bit expensive TT)
