iOS app is a paid app while Android app is free to use. Android app has some premium functionality that includes:
There are 4 in-app purchases for premium functionality:
Any of in-app purchases opens ALL premium features but it allows to pay different amount of money.
Users can pay with Google Play Store in-app purchase or with FastSpring/Paddle checkout if Play Store is not available
When users pays with FastSpring or Paddle he gets license code by email. This license code should be used to unlock premium. It needs to be entered inside Android application. License code expires in 1 day. If users could not activate in 24 hours since he got the code he can restore the code from application.