Check if you have an uncommented directive in your .htaccess like
DirectoryIndex index.php
Also the vhost should have
AllowOverride All
This is kinda old, but the vhost setup seems to be correct.
No, its the right directive. You might be having issues with the hosting provider configuration since you have to pull some settings ad directives from your .htaccess in order to make the Magento run as expected. This is why you set AllowOvrride All in the vhost config. If its a shared hosting or something like that you will have to ask your provider for assistance.
Please check the DirectoryIndex does not have a # in front of it. Also check if the mod_rewrite is enabled with a2enmod rewrite and restarting apache later.
its a dedicated unmanaged centos , i'm the only responsible for every tweak and i do have access DirectoryIndex does not hace # but a line above it do have #default index file cant use a2enmod its centos Thanks