Short on purpose. Almost everything is buyable in Jaipur and Delhi, usually more cheaply than at home.
The weather. Jaipur and Delhi will be roughly 23 to 33 degrees and humid, the tail end of the monsoon. Kasauli sits at 1,900 metres, so around 13 to 24 degrees, and the evenings there are properly cool.
For the wedding days themselves, see the clothing guide.
Beyond that, no need to pack a medicine cabinet. Pharmacies in India are everywhere, inexpensive, and sell most everyday things over the counter.