Im a new member : Understanding the DASHBOARD plugin

Im a new member ! Excited about being apart of this Awesomeness! Im very familar with wordpress but this WPMU DEV Dashboard I need clarification on how this will effect my WPMU Social Site I'm about to create. Here are my concerns and questions,

#1. in my admin area it tells me WPMU Dashboard can only be installed on 20 domains , what does that mean ? does this mean I can only use the plugins that you offer (over 300+plus) only on 20 domains?

#2. Im about to create a WPMU using
*buddy Press
*Pro sites
*Pay to Blog
*Membership
*WPMU Affiliate
*New Blog Templates
****CONCERN: I DO NOT WANT my WPMU DASHBOARD tool to be seen by my community users. The domain name of my social site will be called http://www.XYZ.com ~~ ~~
***Should I install my WPMU DASHBOARD PLUGIN on http://www.ABC.com so that there is no mixup and risk?

#3. When plugins have a new update EX: I will allow members to use some plugins like the WPMU newsletter plugin, ***CONCERN: When these plugins have new version, will my members see notifications in their backoffice saying "WPMU has a new update You need to install the lasted update" Thus making me look slightly unprofessional ?

Thanks