What will happen if an existing subscriber redeem the offer code which is only eligible to new and expired subscribers?

I am working on an iOS app. I have created an annual offer code which is only eligible to new users and expired subscribers. May I know what will happen if an existing subscriber tries to redeem the offer using the offer code url? Then they would finish the whole process through the App Store. There are no ways for my app to block it. Would Apple not allow them to do this?

If yes, would the existing subscribers have to cancel their subscription in order to redeem this annual offer code? If yes, will they then immediately see the offer? Or will they have to wait until their entitlement expires?

Thanks.

Ineligible subscribers will receive a message indicating they are ineligible when they attempt to redeem. It is important when distributing offer codes to your customers that you include the eligibility terms so they know. Additionally to reduce this scenario, it's recommended to distribute the code/url to customers you believe are eligible but the App Store handles it when they are not.

There is nothing preventing from customers attempting to 'become' eligible and attempting to redeem when they are. Good reason to consider offer expiration dates, distribution, etc.

What will happen if an existing subscriber redeem the offer code which is only eligible to new and expired subscribers?
 
 
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