In my app i have several managed products which have a certain price. In the release week I want to make some of them free of charge. As the minimum price on Google Play Developer console is 0.5€, I'm not sure how to make those products free of charge and at the same time save its SKUs to the Google Play servers (as it happens on default purchase flow). I want that, because a user may delete the app and reinstall it later.
Is that even possible?
You cannot change the price of an in-app product once it is published, and you can't sell an item for free. You will have to implement this yourself, maybe by keeping a record of SKUs that a user has access to that is separate from what Google Play gives you. When a user clicks "buy" for a product, pays for it, and consumes it, then add that SKU to the list. If you want to offer a free product, simply add that SKU to the list as well without going through the IAB flow.