WP Robots Txt Allows you to edit the content of your robots.txt file.
Delete all the content from the Robots.txt Content field and save the privacy options.
Yes. Be careful! That said,
robots.txt files are suggestions. They don't really block bots as much as they suggest that bots don't crawl portions of a site. That's why the options on the Privacy Settings page say "Ask search engines not to index this site."