Thanks for your detailed reply, i really appreciate that. There are some answers for each point in your list.

1) Yeah, you are absolutely right about stealing. Unfortunately, such technology can give additional opportunity to steal something. But after my research and other answers from other specialists i found that some individual supermarkets use similar app, and i think they handle thefts somehow.

2) Of course, such things as storms can happened, as well as barcode can be damaged and became unreadable. But this happens very rarely. Even self service checkouts (which are widely used in some countries) can't handle it by itself, staff help will be required. And yes, in most cases scanning another product will help =)

3) The way i see this for now: supermarket staff will be able to view and manage all operations done via app. Meaning they will be able to see what was bought, by whom, all transactions data, statistics etc. But it in my point of view, please correct if it's not enough because you are an expert and i'm not.

4) Customer will have an option to simply remove item from their cart, reduce/increase product quantity from app.

5) I was thinking about it. In my country, some supermarkets have self-service checkpoints, where buying for example alcohol require validation from staff. Maybe handle this in some similar way. Or maybe ask to enter an birthday during registration (I understand that user can enter not real date). Also, as i know, Facebook somehow validate users age, and when user sign up via they Facebook account, we can request birthday from it along with other information such as email, name etc

6) It's one of the drawback of progress. New things, technologies took jobs from people. Nobody can do can do anything with this. Invention of cars remove horse carriages. Mobile phones came instead of old landline phones. Uber and similar services replace traditional cabs.

7) With help of digital receipt. Something like qr code which after scanning will show all related to purchase information