How to know Laravel version and where is it defined?
Is Laravel version is defined inside my application directory or somewhere in global server side directory?
In your Laravel deployment it would be
/vendor/laravel/framework/src/Illuminate/Foundation/Application.php
to see who changed your Laravel version look at what's defined in composer.json. If you have "laravel/framework": "5.4.*", then it will update to the latest after composer update is run. Composer.lock is the file that results from running a composer update, so really see who last one to modify the composer.json file was (hopefully you have that in version control). You can read more about it here https://getcomposer.org/doc/01-basic-usage.md