I was a Peace Corps volunteer in Nepal from 1994 to 1996, so I got to make a few short visits to India, and later one long one. I spent a couple of days in the Darjeeling hill station, touring the plantations and buying tea (to be shipped back home to friends in the United States). Later I took a two-month long bicycle trip starting at the Darjeeling border crossing, into Nepal, across Nepal (stopping for a few days in Kathmandu and passing through Janakpur, Butwal, and Lumbini along the way), across the western border into India, and then south to Agra to see the Taj Mahal. That was the end of my bicycling trip, and I rode a bus back to Nepal.
I think the total distance covered on bicycle was about 1800km or 1300 miles. Any experienced bicycle tourist will tell you that two months to cover only 1800km looks like a very leisurely pace, but I must say, the conditions of the roads and the amount of vertical involved crossing Nepal is a bit more than one might guess. Then again, I must admit, I was always pretty slow.
Certainly I would have liked to have seen more of India than I did, had time and money allowed. I know that there is so much more to the country than just Agra, and it pains me that I haven't seen it and perhaps never will.
As for your other questions, it's difficult for me to answer without writing pages. Would I go back to India? Yes, I would go back again, in a heartbeat. Was the trip enjoyable? Overall yes, though at times frustrating, even infuriating. If nothing else, seeing the Taj Mahal directly is awe-inspiring. I don't think looking at photographs really gives you any idea of what it's like to stand in front of it.
I have never tried geocaching in Nepal or India. I don't think the sport existed in 1996, and sadly, I have not been back to Asia since.