If I'm a teen under 18 (or my child is) can I prevent adults over 18 from connecting and sharing content with me?

Yes, absolutely. Qommunity uses an optional feature called Networks to empower our members to filter the content and communications that come in and go out. You can join as many or as few Networks as you like, one of which is the Youth network for people under 23 years old.

Your account, including your profile and all the content you post (including wall updates) is protected by powerful privacy settings that let you choose where to share/show items to/from Everyone (i.e. incl. the public), Registered Members Only, My Friends and Networks, My Friends, or Just Me. 

To Join a Network:

To Join the Youth Network, or any other, go to your Settings  and select Network Settings. Join (or leave) the Networks you desire by clicking on the button beside the given Network.

Filter Content Coming In:

in Privacy Settings, choose your desired Profile Privacy (who can view your profile) and Profile Posting (who can post on your profile) Settings. Here you can also select whether or not to include you in Member Search results. 

Filter Content Going Out:

In addition, whenever you post anything to Qommunity (wall update, blog, photo, video, page, etc.) you have the option of selecting a privacy setting for that individual post. 

In this way, you could recreate Qommunity into a Youth-only Qommunity for yourself.