tamirind and millets.

Neither tamarind nor finger millet are known from the Indian Neolithic. Some millets were domesticated in India c. 3000BC, and some millets also reached India from East Asia (e.g., foxtail, domesticated before 6000BC in China). African millets (specifically, finger millet) are only known from India in the 1st millennium AD; earlier claims that finger millet was already in India in 1800BC appear to be wrong:

• Hilu, K., De Wet, J., & Harlan, J. (1979), "Archaeobotanical Studies of Eleusine coracana ssp. coracana (Finger Millet)", American Journal of Botany 66(3), 330-333: http://www.jstor.org/stable/2442610

The time of arrival of tamarind in India isn't well known. Shah (2014):

• N. C. Shah, "Tamarindus indica - Introduction in India and Culinary, Medicinal, and Industrial Uses", Asian Agri-History 18(4), 343-355 (2014): https://www.asianagrihistory.org/pdf/articles/nc-shah-18-4.pdf

suggests tamarind might have been taken to India by Ethiopian traders in the early 1st millennium AD, between 100 and 600. However, tamarind was known much, much earlier in Egypt, and known in the Mediterranean in the mid-1st millennium BC. Therefore, it could have travelled to India BC via the land route from the Mediterranean (especially after the Hellenistic conquest of Mesopotamia and Persia).

In the early 1st millennium AD, the Indian ocean was supporting significant long-distance trade and travel (consider the settlement of Madagascar), so there would have been no difficulty for millet and tamarind getting to India then, but that's very post-Neolithic.