How to make in-app purchase, checkout system?

Unity Engine
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1

So I am making android game, recently many game adopts in-app purchasing type item.

  1. How to make in-app purchasing item and checkout system

  2. How to change from demo version(Free) to paid version?
    Normally developers provide 2 type of games, free and paid version. Why?
    Why they just don’t give one free version and if user paid at there, just change the game to full version?

  3. How these can be integrated with unity?
    Is there tutorial page or info?

Thanks.

2

http://www.usethefuckinggoogle.com/

3

I think jvil’s getting a bit rude about it, but I understand where he’s coming from.

leegod, you’ve got almost 900 posts on the forum, so you’re not a newbie like me. Maybe this is your first day thinking about releasing for Android (good choice). You’ve asked multiple questions today that seem like they’d be easy to answer for yourself with some searches. If you don’t understand something specific, then ask that.