problems with hot start

I CANNOT DO THIS BECAUSE I CANNOT INSTAL YOUR HOTSTART... please read messages above

you if now download fresh joomla from joomla.org you will see that session.php is completely same because we don't mess that - we do template.

You can do this simple test - download clean joomla and see if it will install, you can delete if after.

I would rather say that maybe your hosting provider needs to check if suPHP is active and to execute script to rebuild ownership of files and folders.