I want to save data on device itself that would be persistent even after deleting the app and installing it again (data can even be one int/date). According to my knowledge it is impossible because each app can store data only on it's sandbox (I know I can use iCloud etc. but I don't want any services user can not have or give the app specific permissions).
As to my understanding the only option to do that is to store it on my server. But, Apple doesn't allow to send UDID or any other specific device ID and I can't get the iTunes ID. I know I can use any other ID like Facebook ID but the app doesn't have it and that would make a really bad user experience.
I've download apps that does just that successfully (saving data specifically to my device that been recovered even after deletion and without the need to enter any ID or login process). How do they do it? Do they send UDID to some server and apple miss that or there is a way to save data outside the app sandbox?
Well there is the KeyChain, which can store data the would kept even if you delete the app.