The goal was to provide a free application for occasional users and a paid application for people needing more intensive usage. But the objective was to offer to users who tried the free version, to buy the licence without having to migrate their data to another application.
The solution found at this moment was to have a free application "Abcba" limited in operation count storage. And a paid application "Abcba Unlock" which cannot be executed, its goal was to remove limitations of the free version, users of "Abcba" were able to continue to use it with already stored data after purchasing the licence.
A better solution would have been to put in place in-app purchasing of the licence, but this option was not existing for the first releases of the application. Migrating to this solution afterwards was not possible because some people bought the "Abcba Unlock", and there is no way to transform this app purchase to an in-app purchase.
The system of "Unlock" is not provided by Google, it is a custom solution based on communications between the two applications. But for security purposes, Google and mobile manufacturers restricted the communication possibilities between applications. These new restrictions made the "Unlock" system instable on some devices and even not possible anymore on other devices.
The solution now is to go back to a more common model, two standalone applications, a free limited application and a paid unlimited application, this is why "Abcba Unlock" becomes "Abcba Pro", a standalone unlimited application.
Warning! Uninstalling an application removes all its data, all events not imported in "Abcba Pro" will be lost as soon as"Abcba" is uninstalled! If you are not sure you can do a backup using the "Export" option in the main menu.
By the way, it is highly recommended to activate automatic backup to Google Drive for all events, there are so many situations leading to data loss (mobile stolen/broken/lost, wrong manipulation, ...)