CI4 lifecycle : What is the loading point of Common.php

I have developed an Ecommerce application using pre-release version of CI4. In that application I have used "service" in Common.php (inside app) file without any issue. But after updating to 4.0.3, the availability of services in Common.php fle is missing. Even, I can not use base_url() in Common.php. I think the entry point of Common.php in CI4 lifecycle has been changed.

Could anyone help me please by providing me the CI4 lifecycle and the loading/entry point of Common.php?
Thanks in advance.

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This file including in System/bootstrap.php in the same way as in RC-1 in which the App/Common.php file appeared.
index.php -> System/bootstrap.php -> App/Common.php & System/Common.php