StoreKit2 AppTransaction originalPurchaseVersion

I am looking to move from paid app to fremium without upsetting my existing users. I see WWDC2022 session where new fields introduced in iOS 16 are used to extract original application version user used to purchase the app. While my app supports iOS 14 and above, I am willing to sacrifice iOS 14 and go iOS 15 and above as StoreKit2 requires iOS 15 at the minimum. The code below is however only valid for iOS 16. I need to know what is the best way out for iOS 15 devices if I am using StoreKit2? If it is not possible in StoreKit2, then how much is the work involved in original StoreKit API(because in that case I can handle for iOS 14 as well)?

StoreKit2 AppTransaction originalPurchaseVersion
 
 
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