will users keep their forum post count
No, they will be counted separately for each site. But you can manually increase the number of posts for each user.
lets say after some time we delete bodescu.ucoz.com, will this cause all of the users to be lost from realhiphop4ever too
If realhiphop4ever is the administrator of your community then the users will be saved.
I'm not active on the forum anymore. Please contact other forum staff.