My iOS app currently offers an auto-renewable subscription A. I want to add a second subscription option B with a discounted rate. Option B shall only be available for users who bought a certain upgrade X via in-app purchase in the past (that in-app purchase is not offered for sale anymore).
How can I prevent that users subscribe to A and then switch to B in the System Settings? Users who didn't purchase X shouldn't even know that B exists.
As far as I understand Apple's documentation and App Store Connect Help, users can upgrade/downgrade/crossgrade between subscriptions in the same subscription group. I assume that by adding the subscriptions to two different subscription groups, switching between A and B is not possible, but I couldn't find a definitive answer on this.
If a user starts any subscription, will they automatically see all subscription groups in the System Settings, or just the group with an active subscription?