Yes, you can buy Alcohol on arrival at Amritsar airport. The Duty Free shop is located in the baggage re-claim area (you can't miss it).
You can obviously buy duty-free goods on departure from the airport too. The 2nd Duty Free shop is located immediately after immigration and security control. Here's a photo of it:
http://i220.photobucket.com/albums/dd34/pendoo/ATQ22.jpg Hope this helps...