Can I use external payment gateway for app purchases

Hello, we have an app in which you have coins. Those coins can be used in iOS app, Android app and the web application for messaging another user. Questions:
  • Can we use external payment gateway and the in-app browser to make the purchase for the coins?

  • Can we accept payments from our WEB app and provide the purchased coins to the iOS use account. ?

  • If user purchase coins from IAP can they be used in the Android or the WEB application in terms of Apple legal matter.



Thanks In advance.
Can I use external payment gateway for app purchases
 
 
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