My black Mollies are around 2 Inches..im sure they get bigger..but im not sure about exact size..
they can have upto 90 babies...but usually around 40-50 is more common depending on the size of the female and whether or not its her first batch. Dont expect many fry if its the first batch. As for time of the day...i dont think they have a particular time of day when they give birth...most of mine have been through the night...but ive had some during the day.
Hey gup gup! Your molly will be really fat and they usually have 10-40+ fry (babies) and they can have them any time of day and you may want to move her in her own tank if shes really big and remove her when she is done having babies.Good luck!