What all characters will be avaliable?
Play Overlord H (the old completed one) to get an idea of all characters available, it's quicker to ask if specific characters will be available.
Currently, as of R2, there are only Shalltear and Albedo. R3 will have bigger scenes for Albedo, and introduce Solution (she'll have roughly the same amount of scenes Shalltear/Albedo currently do in R2).