On what basis, stocks are graded as "A", B","S","T" AND "Z" in the indian market

I never heard of ratings of A B S T Z but I am personally not too familiar with Indian markets. But knowing analysis I know how the process is usually whether it's in the indian market or any other country. All the ratings are basically given based on the company's financial performance. Credit risk, default risk, liquidity or solvency risk are the main aspects of rating. Some of the questions that the analysts guide toward ratings are:
-can the company meet its short term obligations/long term obligations?
-are the company's financials accurate, unanbiguous and easily understood and without any manipulation?
-is the company as profitable as previous years? If not then what is causing the loss? If sales or any margin is affected, that is definitely worrisome.
-how is the company overall compared to its peers in the industry financial wise, profit wise?
-how is the company leveraged? Do they have any long term debt due soon and how will they pay that?

these are some of the questions that analysts answer to analyze companies, cities, countries...