-What should I do if nobody challenges me?
That's simple: take the initiative and challenge someone. If people decline that challenge, then it's possible that you may need to improve and revise your RHG to meet standards and make it more appealing.
-Does my story have to be in any specific length?
Though there is no set length that a story/about section has to be, we suggest that you put a little bit of thought into it; nothing looks lazier than "He has no past." It ultimately just makes you look apathetic.
-What happens if somebody challenges me?
If somebody challenges you, you negotiate the due-date for your rhg battle, and then the two of you animate each others rhgs in your own battles. After that, you post both of your battles in the Battle Zone with a poll thread, and the community decides the victor.
-Can I make more than one demo for my RHG?
Absolutely; I'd even go as far to say that it's encouraged. Multiple demos makes it look like you put more work into your RHG, as well as making certain powers and abilities more clear and understandable for those who might be viewing your thread.
-How do I gain/lose points?
You can't lose points; however you gain winning points through victories and losing point through losses. It should be indicated on you thread like so: (e.g. 2 wins, 1 loss) 2/1