Wordpress Themes - WP Forum at BFA - PHP Fatal Error: undefined functions get_template_part and post_password

Hello,
I found in my server log some interesting messages:
1.

Code:

[Fri Sep 18 15:18:53 2015] [error] [client 162.216.19.183] PHP Fatal error:  Call to undefined function get_template_part() in /home/piotao/PKB/www/wp-content/themes/montezuma/index.php on line 1

and here is the index.php file mentioned in the call:

Code:

<?php get_template_part( 'head' ); ?>

</head>

<body <?php body_class(); ?>>

                

        <?php 

        global $montezuma, $wp;

        // - use custom template if set ( for post or page )

        // - or else, according to WP Template Hierarchy

        $tpl = bfa_get_virtual_template();

        echo bfa_parse_php( $montezuma['maintemplate-' . $tpl] );

        ?>

        

        <?php wp_footer(); ?>



</body>

</html>

... and this error is connected to the server invocation with the following requests:

Code:

162.216.19.183 - - [18/Sep/2015:15:18:53 +0200] "GET /readme.html HTTP/1.1" 200 7360 "-" "Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.2) Gecko/20100115 Firefox/3.6"

162.216.19.183 - - [18/Sep/2015:15:18:53 +0200] "GET /wp-content/themes/montezuma/ HTTP/1.1" 500 - "-" "Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.2) Gecko/20100115 Firefox/3.6"

162.216.19.183 - - [18/Sep/2015:15:18:53 +0200] "GET /wp-admin/js/common.js HTTP/1.1" 200 24619 "http://sucuri.net" "Mozilla/5.0 (compatible; MSIE 8.0; MSIE 9.0; Windows NT 6.0; Trident/4.0; InfoPath.1; SV1; .NET CLR 3.8.36217; WOW64; en-US)"

2.
Another error I've found today is this one:

Code:

[Sat Sep 19 13:11:54 2015] [error] [client 87.255.66.244] PHP Fatal error:  Call to undefined function post_password_required() in /home/piotao/PKB/www/wp-content/themes/montezuma/comments.php on line 4

Here is the code from this file:

Code:

<?php 

global $montezuma;



if ( post_password_required() ) : 

        echo bfa_parse_php( $montezuma['subtemplate-comments-password'] ); 

        return; 

endif; 

...

This error was caused by the request:

Code:

87.255.66.244 - - [19/Sep/2015:13:11:54 +0200] "POST /wp-content/themes/montezuma/comments.php HTTP/1.1" 500 - "-" "Mozilla/5.0 (Windows NT 6.0; rv:16.0) Firefox/12.0"

How to get rid of these errors?