NOT small but as long as they both fit and have enough space to walk around in they should be fine.
The ideal size for a hamster cage housing three hamsters is at least 2 square feet. Hamsters are fairly compact creatures and generally do not need too much room to survive and be content.
Just one. (1)
1+2+4+8=15 There can't be half of a hamster. Start with the smallest cage with the smallest amount possible:1
Stick them in the same cage over night
no
No because if you put them in the same cage they will fight with each other. It is best if you keep one in each cage. Unless they are dwarf hamsters. Than you can put them in the same cage.
It is recommended to have only one hamster per cage to prevent territorial disputes and fighting. Hamsters are solitary animals that prefer to live alone, so it is best to provide each hamster with their own space and resources in their cage.
you cant till they are 2 weeks old
Every 1 week clean his or her cage.
I'd probably say that it is better to keep two females together as males can become very competitive and are more territorial. If the female in either case becomes pregnant, then the hamsters need to be separated. The mother will kill her offspring if she is disturbed, so it is very important to put the cage in a quiet, undisturbed area, away from other hamsters.
I usaually stick them in the same cage over night to make it faster!
Six, because the question didn't mention someone taking their body out of the cage.