Hi!
About macochan's graduation, I'm a little sad, but I think that everyone was aware about this. Since a moment she wasn't talking about the group activities but about her own activities (emissions, photos....). Also her role was less important in the latest songs. So it's not very a surprise.
The group will probably stay like that for a moment, since they all started to play instruments (more or less importants
).
About Sako and Saki, they are not so similar (eyes and mouth are slightly differents). They are just young and cute Japaneses girls.
About Instagram accounts : yes, they are officials.
Mio started her account since a moment and announced it on Twitter, and then Naomin, Yucky, Natchu and Morishi started one (in this order), and they announced it on twitter too.
To finish, iIwould like to share with what will probably be the photo of the next album ("5 Shunen Kinen Best", coming December 10), and a new uniform ^^ :