Are student's allowed to make twins as a characer (as in have two student characters as part of the bio who are biological/identical twins who both applied to join Shokushu and generally remain together) and play them as such?

It'd be really difficult to pull off in my opinion... but if you think you can do it, give it a shot.

How about four students that I intend to play together as a single player in the same threads as one another, the four are simply friends applying to Shokushu together and all ended up in the targetable selection, not related to one another in any way? Do the four of them need to be posted in separate threads, can I make a single profile for all of them or is it fine if I post all four of their profiles on top of one another?

I apologize for this apparent necro-ing, but it seemed to me that this thread would be where this question belonged.

You would need to be posted into separate threads, mostly because there is a character limit for posts. Though I do admit.. that plan does sound quite complex to pull off to be honest.

Ah, if it is character limit that is the problem, I could post the four profiles in separate posts directly after one another. This way it would still just be one post each.

Also, each is pretty short, so Andramica's profile with Hibernator is actually longer by itself, so room is not a problem. Except that three-image per post limit, which could be troublesome since there are four girls with an image each, but...

Haha.

First of course, biological twins cannot play any sort of incestuous scene.

As for the rest, it would certainly be confusing but if it's in a closed roleplay with the OOC consent of who you are playing with, that is between the two players. In general posting, one char per post to avoid confusion.