How is india distinct from the rest of asia?

There are a number of differences. One of them is the culture : India has a very specific culture (and of course there is a lot of variation within India, but there are a lot of similarities too) and religion : Hinduism, which is almost absent outside of India. Further, many  Indians have a different appearance than other Asians :brown skin, especially in the south. Also, Indian languages, although also very varied, provide a sense of unity, since they all influenced each other over the years  (so while tamil and Chinese are both different from Hindi , Tamil has borrowed more from Hindi than Chinese.