if I delete a product, can I use it’s barcode again on a different product? and if we are required to reuse barcodes, how could we ensure it wont get old data?
No because even if you delete the product at your end it still remains as part of Amazon’s catalogue and will cause problems down the line.
If a listing is created using an EAN (barcode) then that is retained on the database even after you delete your listing, so you can’t reuse on a different product as it’s linked to the Amazon ASIN for that product.
If you are the only seller and created the original listing using your own EAN, then you could change the listing detail retaining the same EAN, but better to use a new EAN for a different product.