Answer 1. I can only help withjust tried doing the question aboutbackup and restore feature from the captchaMagento Admin Panel. Magento is putting the store into maintenance mode using the maintenance.flag method. This involves creating a blank file in the sites root directory called "maintenance.flag" once the backup or restore is complete this file will need to be deleted.
Answer 2. In the 1.9 RWD Dev Guide they say that RWD was not implemented for captcha, I'm not sure why.
It has been disabled by the use of a blank captcha.xml file in the following directery: /app/design/frontend/rwd/default/layout
If you delete this file it will revert to the one in base/default theme. I can't see a reason why leaving captcha on would cause any problems.