DW Question & Answer Pro is an all-time favourite question & answer plugin for WordPress. Your WordPress site will have a full-featured question & answer section like StackOverflow, Quora or Yahoo Answers.
Demo: https://codecanyon.net/item/dw-question-answer-pro-wordpress-plugin/15057949
source http://www.codelist.cc/plugins/244038-dw-question-amp-answer-pro-v128-wordpress-plugin.html