How can I trade in USD & INR and during which best
trading hours as per Indian Standard Timings please?
Use the brokers who offering this trading pair! Personally, I don’t use this type of exotic trading pair!
Articles I found using a Google search
https://www.motilaloswal.com/article.aspx/1324/Learn-how-to-trade-in-USD-INR-Pair-Contract-in-Currency-Market/
A List of Brokers Offering the USD/INR Pair for Trading
The spreads offered vary widely. You want a reputable broker with the lowest spread. Make sure that the broker you choose is regulated through a reputable regulatory body. Deposit a small amount and make a withdrawal to see how this process is handled.
Let us know how you make out and what you learn about this. Good luck!