How can I stop Lightroom 6 importing duplicates?
You need to check the "don't import suspected duplicates" option under File Handling panel in the Import window.
does that exist in Lightroom 6 Chetna?
yes, it does.
Make sure you have the latest update of Lightroom.
You can download 6.3 version from this link : Keeping Lightroom Up-to-Date
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