1. PHP REQUIREMENT LINK: https://book.cakephp.org/5/en/installation.html and also check /vendor/composer/platform_check.php
2. Set "DEBUG" true in  "config/app.php"
3. We have copied logs folder from older version inside our package. As it throws error.(Log folder added in version 4.0.2)
4. We have added database settings in app.php file explicitly in version 4.0.0 i.e,
'host' => '[[softdbhost]]',
'username' => '[[softbuser]]',
'password' => '[[softdbpass]]',
'database' => '[[softdb]]',
as they were not present in version 4.0.0, and they are needed to connect to database. Please check in next version.(If not present add them below the line 'persistent' => false, under ORM settings in app.php file).(Not needed since 4.0.2 as script now uses app_local.php for configuration and provides way to configure database settings.)
5. Use app_local.php and not app.php for configuring database settings in manual installation(As settings in app_local.php override settings in app.php)(Since version 4.0.2)