Question about changing a paid game to freemium with IAP

If I decide to change my paid app to a freemium w/ IAP to unlock the full game, what would happen to the users who already purchased the game when they update the app?  Would the restore button come in handy in this case or how does that work? 

Have you considered just having a 2nd app?  There would not be a good way to know if someone already had the paid app that would be safe if they deleted the app.

If I decide to change my paid app to a freemium w/ IAP to unlock the full game, what would happen to the users who already purchased the game when they update the app?  Would the restore button come in handy in this case or how does that work? 

It works quite well in my app. See the purchasing example on how to implement it, then add product identifier checks in the “purchase success” and “restore” sections to check for what the customer bought.

I implemented both one-time (non-consumable) and subscriptions, but the latter may need a special subscription checking. Look at the example by Ganesan:

https://github.com/ganesan/Auto-Renewable-In-App-Purchase-Validation-using-Corona-SDK

You may want to use a better base64 implementation, but it shows how to handle the receipt and shared secret password. I don`t know how often you want to check the renewable as it tends to ask the user for iTunes login/password, so you may want to store the subscription period on the device and only check if its a new install.
 

Have you considered just having a 2nd app?  There would not be a good way to know if someone already had the paid app that would be safe if they deleted the app.

If I decide to change my paid app to a freemium w/ IAP to unlock the full game, what would happen to the users who already purchased the game when they update the app?  Would the restore button come in handy in this case or how does that work? 

It works quite well in my app. See the purchasing example on how to implement it, then add product identifier checks in the “purchase success” and “restore” sections to check for what the customer bought.

I implemented both one-time (non-consumable) and subscriptions, but the latter may need a special subscription checking. Look at the example by Ganesan:

https://github.com/ganesan/Auto-Renewable-In-App-Purchase-Validation-using-Corona-SDK

You may want to use a better base64 implementation, but it shows how to handle the receipt and shared secret password. I don`t know how often you want to check the renewable as it tends to ask the user for iTunes login/password, so you may want to store the subscription period on the device and only check if its a new install.