You can figure the area yourself by using the forum area = pi x radius squared. I’d say you could have up to maybe 20 or 30 hives, maybe more, all set close to each other in your bee yard, and except for the occasional “drift” (where a few bees go to the wrong hive) there should be no problem. read more
As close as you want. The photo below is a good example of hives close together. This is actually a mobile bee house in Slovenia that can be moved from field to field. Here in the United States migratory beekeepers place whole pallets of bees in fields and orchards. The bees manage to find their way back home. read more