1. 
PHP: mysqli_result::free – Manual
www.php.net/manual/ru/mysqli-result.free.php
2.
PHP mysqli_free_result() Function
www.w3schools.com/php/func_mysqli_free_result.asp
3.
MySQL :: MySQL PHP API :: 3.10.15 mysqli_result::free…
dev.mysql.com/doc/apis-php/en/apis-php-mysqli-result.free.html
4.
php – Warning: mysqli_free_result() expects… – Stack Overflow
stackoverflow.com/questions/31557639/warning-mysqli-free-result-expects-parameter-1-to-be-mysqli-result-boolean-g
5.
PHP mysqli – MySQL programming in PHP with mysqli extension
zetcode.com/php/mysqli/
6.
Getting Data From MySQL Database
www.tutorialspoint.com/php/mysql_select_php.htm
7.
PHP MySQLi Prepared Statements Tutorial to Prevent SQL Injection
websitebeaver.com/prepared-statements-in-php-mysqli-to-prevent-sql-injection
8.
PHP MySQLi Functions: mysqli_query, mysqli_connect…
www.guru99.com/mysql-php-and-other-database-access-methods.html
9.
3.8.37 mysqli::query, mysqli_query
docs.oracle.com/cd/E17952_01/apis-php-en/apis-php-mysqli.query.html
10.
Ограничение количество выводимых записей MySQL
wm-school.ru/php/php_mysql_select_limit.php
11.
PHP | MySQL LIMIT Clause – GeeksforGeeks
www.geeksforgeeks.org/php-mysql-limit-clause/
Conclusion
Guide above should be useful for Mysqli_free_result.