I never really had a problem purchasing alcohol from duty free and bring the purchased item to another location. Normally theres a limitation requirement and after purchasing it they will either have it ready in a bag for you before you board the plane or will let you carry it on. Actually, you can even purchase duty free alcohol on the plane while traveling abroad, just remember to know the limitation requirements and there shouldnt be a problem. Again just replying to your post from previous experience. Oh and a little tip that might help; If you're just purchasing duty free alcohol thinking to get the best deal then make sure you research on prices at different locations (in your case the places youre headed) on the type of alcohol you're planning to purchase because it might not always be the best deal in duty free.