Depends really on when and where you go. India has got some nice unpolluted places, and it has Delhi, around November (when the people a state downwind burn crop stubble).

On the cleanliness issue, all we can really say is that we are trying harder! The railway system used to be very dirty, it is much much cleaner now.

Food hygiene can be a problem for those not used to it, but standard common sense rules like eating in crowded places should keep you safe.

Oh, and we don't have a habit of demanding you to register with the police when checking in to a hotel unlike some other countries.