Hi, yes 4 nights is a good enough time to explore Singapore. i'm attaching with this comment a itinerary to explore singapore in 5 day. You can go through it and plan your trip.
Hi
I would say there is a lot to do in Singapore, so choose as per your interests, if you want to cover it all add a day or two. We recently visited for 4 days and felt that another day here would have added more to experience. You can check our Itinerary here https://www.renegaderunaways.com/blog/detailed-itinerary-for-a-trip-to-singapore If you have any more questions, I can help
4 N is too long dear, i think you should vistin to another country such as Indonesia ,, they provide free visa on arrival for indian passport holders and you will get cheap flight from Singapore to any city of Indonesia Happy travelling??