Q&A Plugin for wordpress site

I would like to add a Q&A plugin in wordpress format. I am open to the theme because Q&A will be the primary purpose of the website at this point. I basically need: Landing page with 4 key sections - Search database (of existing questions) - Review Q&A by category (it is expected that 10 categories are added which for now can be called Category 1, Category 2, etc) - Post question - Last questions (last 10 closed and last 10 open) Key functionality I am looking at (which I believe is standard of most Q&A plugins/themes: - Everyone can read all Questions and answers - Only logged in users can post questions and anwers - If answer was helpful the user who has posted the question can close so it is marked completed - Ideally the user who gave the "right" answer get a reward so can display most helpful users of last month. This is nice to have but not mandatory at this point. Important is that the theme/plugin looks professional as it is supposed to be used for beta testing as an MVP/prototype.