Create a iOS app to demonstrate the use of consumable produc

We consider using consumable products in our next app to allow users to set packages of content free until there is no more content. We never used consumable products before and we would like you to create a example app that demonstrates how this works internally. It would be sufficient if the app works against apples sandbox. The aspect of restoring past purchases in case of a reinstall is of special interest to us as the apple guide states that you will have to handle the restore on your own. Unlike how it is done with normal products. An extra problem, that we would like to see solved is how to change the products and still allow the users to restore the old purchases when they reinstall. It will be part of the project to document how the app is working (including any severside code that might be needed). To describe the function with an example, lets say our app contains 1000 items. The user can buy 10 items at a time. To get all items the user would need to buy 100 times. Standard products seem unpractical for this as we would need to register 100 products with apple. Using a consumable product we could do the same with just just one product and the user buys this product 100 times to get all items. But we do not know how to preserve how many items were already bought if the user reinstalls the app or installs it on a secondary device.