How to implement a paid Android application?

Question

Android

what is easier to do
1. upload 2 applications to the app store, one is free with limited functions (I can limit functions including the server), the second is paid without restrictions,
or
2. one application that will open additional functions after payment
???
What is the easiest way to make payment? through google play or through which payment system?
what is the further algorithm after the callback of the payment system has worked about successful payment?
the application has a server part, the API of which needs to be "reported" about the payment

Answer 1

through google play or through which payment system?

Only through google play. Otherwise, the application will be banned.
If you implement 2 applications, then you don’t even need to write the code, it seems - the full one will be downloaded immediately.
If you implement 1 application - after the purchase, just raise some kind of flag and remember it - and it checks whether the full version is not.

Answer 2

Option 1, suitable if you have written an application and 100% will no longer make changes there.
Otherwise, you will have to support 2 versions of the program
2 - the variant is more preferable because the application will be one.
3-If you decide to make a paid application, then the standard purchase mechanism is ideal for you. If you decide to make an in-app payment, then the standard in-app payment mechanism is perfect for you. If you do not want to give 30% of Google's earnings, and are going to use something else, then in the API description of this something else, there is detailed information on how and what to do. It looks like this id =10 -> payment system ->on completion of the transaction http:\\your server\response processing file.php?pay_status=ok, id= 10, and then enter this information into the database. The mobile client accesses the database and, realizing that the payment has passed, opens access to the paid functionality
And now life:
Young developers often have the illusion that I wrote something and now millions of people will buy it. This is not so unfortunately. People tend to buy well-made applications, and what would make you need experience + experience of interaction with users. I don’t know what you are doing there, but I recommend that you first upload a free version with full functionality and cut it until users have no wishes for its improvement, and after that make this functionality paid.