1. For next release kindly check upgrade method.
2. From 2.5.2 we have given update from just previous version i.e. 2.5.0. For next release kindly check if it gets upgraded by normal process.
3. Auto upgrade might need some changes when there is a new version with changes in database. Add the steps accordingly in upgrade.php
4. PHP REQUIREMENT LINK : install/install_functions.inc.php
5. Select Timezone = America/New_York in manual installation.
6. for adding new language download language from https://www.hesk.com/language/ link and open text.php and get values of "LANGUAGE" ,"EMAIL_HR" and language file name ex. "ar" from ar.zip ( FILENAME = ar ) and arrange in this format and add in $hesk_settings array
'{{FILENAME}}' => array ( '{{LANGUAGE}}' => array('folder' => '{{FILENAME}}', 'hr' => '{{EMAIL_HR}}'), ),
7. Since 3.5.0 version we have removed auto upgrade because the script was using ajax to migrate the customers.