added Reimu and Marisa since they appear in the middle at the back. I'm pretty sure Suwako is parodying something but can't tell.

and,what kind of robot is that one by the "heroines" side?

It's got a "snake" sitting by its head, and it's got something that looks like Kanako's rope circle on the back. I would guess that it's connected to the Moriyas in general, but it's hard to say.

The mech is a custom portrayal of Hisoutensoku, a "toy" of Suwako's apparently, if this is what you're asking for.

Who's the guy in the top-left of this pic?

I think it's supposed to be Suwako.