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Let's say I want to build (iOS + Mac) free app which unlocks full functionality for paid subscription via in-app purchases API. To encourage natural growth, I would like to implement a referral program, similar to what apps like Uber have: 1. User invites their friends to my app (using a unique link or promo code) 2. Then for each activated invite they both (user who invited the friend and friend who used the invite) get a free month of access to premium version of the month.Is there a way to implement such a system with App Store and Mac App Store? Is it even allowed by IAP guidlines? (I suspect not). Now, let's say that this ideal system described above is impossible to build according to guidelines or tech limitations, but an alternative is to offer a free month of access only to users who used the invite. The user who originally sent the invite could get something else outside the app, let's say a free sticker if 10 of his friends signed up. This is easier to build and I think it doesn't contradict any guidelines. What do you think?A reply from Apple representative would be extra valuable. Thank you for your help.