Can an Android / IOS single app have both Subscription and Full Purchase Methods?

I am new to Android / IOS apps development with React Native. I am using react-native-iap to implement in app purchases.

I want to know whether an Android / IOS single app can have both Subscription and Full Purchase Methods ?

If yes, what will happens

1. When user first subscribed the app, and then try to purchase the full app ? will subscription get cancelled ?
2. When user purchased full app and try to do a subscription ?

Thank you.

Subscriptions and "one-time-purchases" are different.

When you buy 2 subscriptions, you can manage the replacement of one by another one. Although, the behaviour is different in iOS and android:

• On the Apple App Store, you have the notion of "subscription group". If you try buying another product in the same subscription group, the previous subscription will be automatically replaced by Apple (at the next renewal date for a downgrade, immediately for a crossgrade/upgrade).
• On the Google Play Store, you don't have this notion and you'll have to manage the replacement by yourself (more info on this here: Allow users to upgrade, downgrade, or change their subscription)

When you want to replace a subscription by a one-time-purchase, you can manage the "replacement" manually on the Google Play Store, but not on iOS:

• On Google, you have an API to cancel a subscription: use it after your user buy the "full-app"
• On Apple, such API doesn't exist and the only thing you can do for now, is explaining to your user the different steps to cancel his subscription. You can help him with this deeplink: https://apps.apple.com/account/subscriptions

Opening this URL launches iTunes or iTunes Store and displays the Manage Subscriptions page where the user can upgrade, downgrade, or cancel their subscription by disabling auto-renew

Concerning the full app => subscription, I don't know. You could refund the purchase, but it would mean you would have lost money during the corresponding period of time.