You mean a sparse enough area? I've generally found dense areas are more homogeneous while even neighboring villages in sparsely populated areas with bad roads and no telecommunications tend to be very different. Makes intuitive sense since transmission of culture is easier.
Not really. In dense areas, you often have far more diverse populations, as cities attrat people with different traditions and backgrounds. But in a place with as many social groups as India, these people often maintain many of their customs and habits even in the dense urban context, resulting in a great variety within a small area.
Within the same city, the Hindu majority areas will look and feel noticeably different from the Muslim majority areas. The culture, and sometimes even language, is different.
And if you are in a dense enough area, it can change every 2km, when accounting for differences in socially conditioned dialects and customs.