Question

Does the final published app requires the same version for In-App Billing as the testing one:

the version number of the uploaded application must match the version
number of the application you load to your device for testing

http://developer.android.com/guide/google/play/billing/billing_testing.html

This would be a problem if the users with the old app versions cannot pay to unlock their demo game into the full mode, for example.

If this is the case then whoever would try to unlock his demo game should get the message to download the latest version first before the purchase, rather than an error message such as:

“Application Error : This version of the application is not configured
for Market Billing. Check the help center for more information.”

Any suggestions about the best way to deal with this?

Answer 1

I have going throw this every time I’m publishing a new versions of our apps. Solution is simple – just upload apk file with same version you are testing now (with BILLING permission, signed with your release certificate) as draft to your Google Play Developer Console. To do this click on your apps name in apps list in Developer Console, click “APK files” tab, next click “Upload APK” button, choose your new apk from your local computer, upload it, then click “Save” button in upload dialog, and don’t forget to click another “Save” button in upper-right corner of “Edit Application” page.

After that, you will see two sections in “APK files” tab – Active and New. There will be a link “Activate” near your newly uploaded apk also. But do not click it until your will be ready to publish your new apk to users.

Please note, you may need to wait up to a few hours until new version of your apk will become active and “This version of the application is not configured for Market Billing” error message disappear.

Regarding proof for this from official sources – this information presents in a link you have provided in your question:

Upload your application as a draft application to the publisher site.
You do not need to publish your application to perform end-to-end testing with real product IDs; you only need to upload your application as a draft application. However, you must sign your application with your release key before you upload it as a draft application. Also, the version number of the uploaded application must match the version number of the application you load to your device for testing. To learn how to upload an application to Google Play, see Uploading applications.

And I can sure you from my own experience this method is works.

Users with older versions of your app still will be able to use your app, and still will be able to buy In-App Purchases even after you will publish new version of your apk.