Sorry to go off-topic, but I had not come across the concept of Indian city tiers before, and found it interesting.
https://en.wikipedia.org/wiki/Classification_of_Indian_citie...
https://en.wikipedia.org/wiki/Classification_of_Indian_citie...
The usual usage is just:
Tier 1: Metro cities, the ones you've likely heard of. Mumbai, Bangalore, Delhi etc.
Tier 2: Cities, but much smaller population-wise. These are the cities that are getting newer airports for eg. Most state-capitals would fall here. These count up to around 50 to 100 depending on who you ask. Linked to national highways usually.
Tier 3: Small urban towns. Population is usually a few lakh (1 lakh=100_000) at most. (<300k or so).
It more-or-less corresponds to the X/Y/Z usage on the wikipedia article.