simple app development

I want to develop an app that will be free but have a single in-app purchase. I want the users who buy the in-app purchase to get a special message which the app displays with a unique identifying code, so that no user gets the same code and each code is tied to a specific user. when downloaded, I want users to be able to see a list of all the users who have purchased the app and to be able to see the unique code that is tied to the app as well as the amount they paid for the app. So, in simple terms: User downloads app for free When user opens app, they can create account with their name. There is only 1 page with a simple list that displays all users who have purchased an in-app purchase, the list should display user name, amount purchased, and code. there should be a single purchase button, which can be clicked to make a purchase. When a user makes a purchase, the app should generate a unique code for that user, as well as put the user on the main list which all other users can see. The list should rank users, with the user who paid the most in in-app purchases at the top.