@hightor,
Thanks for being patient with me.
however, I still have one question left.
So, if the word dare is used as a main verb and not a modal verb in the phrase "Who dare challenge me?" then does this mean that phrasing it this way would also be correct? "Who want to challenge me?".
Since you stated that who is an interrogative pronoun and that it can either be singular or plural, I'm assuming "who want to challenge me?" Should also be correct.
I can give another example. Here: "Who want these candies?"