As no one has replied I will attempt to answer your question
I do not know which rate ET Now is quoting hopefully some other member will tell you.
Now regarding your question about the gap. I do not trade USD/INR however gaps are very commonplace if you trade on an exchange.
Gaps are not commonplace but still do occur from time to time as weekend gaps if you trade OTC forex.
Reason is forex trades 24 hrs a day 7 days a week you can even place trades on weekends although spreads will be very high due to low liquidity as there are fewer market participants
So what happens on an exchange is say trading opens at 09:00 and say trading closes at say 17:00 now although the exchange is closed trading on the OTC market still continues and prices will move by the time the morning comes and the exchange opens for trading again at 09:00hrs the opening price will be at (or very similar) to the OTC forex price so this appears as a gap compared to the closing price on the exchange
In essence there is no "gap" at all it just appears that way because the exchange was closed for trading and when it opened prices which were trading throughout the night have moved away from the last traded price on the exchange. However when the exchange opens the opening bids/asks will be very close to the current OTC Forex price and this appears as an overnight gap.
Occasionally the opening price on the exchange can also be different from the current OTC forex price but this phenomenon is rare and even if it does manifest it will be exploited by arbitrageurs who will step in and the price will return to somewhere near the current OTC forex price.
My english is not very good but hope i was able to explain somewhat and answer your question