I just want to know why draught beer tastes so different at different places in India. I have been to different places all over the country and the beer tastes radically different.
It's many smaller factors but the most likely if it's the same brand are the following:
Storage temperature: in shipping and storage large temperature swings or storage above cellar temperature increase the ageing process of the beer dramatically. In extreme cases of hot temperatures spoilage bacteria, as well as chemical changes, are even more prone to happen.
Draft line cleaning: every bar has different ages on their lines as well as different cleaning standards. In high end beer bars, line cleaning is encouraged every two weeks. This removes mineral buildup as well as destroys bacteria growth in plastic lines for a time. These buildups or bacterial produced off flavors will be different to each location and can easily ruin beer, or at least change its intended flavor.
It's all in the water. The water has a big role in the beverage's taste.