Play Store In App Purchases

I have an app that uses Microsoft Azure for text translation. I want to sell a 'basic' version on the Play Store for $2.99, that comes with a limited number of translations (30 translations), once the user reaches that limit my app will disable the translation function, then the next time they try to translate something I want the app to prompt them for an in-app purchase with three options, $2.99 pay as you go, $9.99 per month subscription for X amount of translations and $19.99 per month for unlimited translations. I need someone who is very familiar with using Play Store's required system for in App purchases ... and the main thing is after the user purchases one of the plans ... some kind of key has to be returned back to the users App to switch the translation functionality back on and control the translation usage based on which plan the user purchased. If anyone out there already knows how to do this kind of thing I would love to hear from you.