Q&A plugin - suscribe to questions feature

Hi wpmudev. I have 2 questions regarding q&a plugin.
1) How does the suscribe to questions feature works? Can users suscribe to the questions is particular they want to? Or only to new ones?
2) Is it possible not to allow the same question to be asked twice, like quora? If someone want to ask something, can the plugin check if it hasn't been answered yet?
Thanks a lot!