Just a heads up while traveling to India.
While most international airports adhere to a common understanding that once you have passed customs control and have entered the transit duty free area, all items purchased in duty free get sealed in a specific bag with the purchase slip as proof and are then allowed to be taken with you through security checks at any transit airports you may be passing through. (provided you remain in transit)
However, NOT Mumbai airport.
No matter if you are just changing airlines and heading off to your final destination, security at this airport will not allow you to re-board your on-going flight with any items that do not meet the standard security criteria. So that bottle of expensive cologne that exceeds 100ml or the bottle of Gin you bought at duty free just before you first took off; you will need to destroy them all before they will let you continue to your destination country regardless of the proof you have of the duty free sealed bag and the purchase slip, there is just no reasoning. But they are quick to note that you may proceed through to their duty free and buy the very same items, and take them with you.
Although this defies common logic, I know, this is just the way it is, and I wish I had come across a post like this before my trip as it would have saved me some cash.