Authenticates users through Active Directory.
Yes. This plugin only supports Active Directory bind and can not be garuanteed to work with LDAP.
No. All searches are based around Active Directory search functions and should be tailored that way.
This plugin has a built-in debug mode.
WP_DEBUG is enabled in
wp-config.php, it will turn on the notices that some authenticatin information are added on the log entry.
If you don't know how to define the constant, see WordPress document.