Can we please get an option to invite to game when hovering over a friend on friends list?...

This is not the place to get an invite. Please ask a friend on your friends list for a invite if they are in the preview program.

One other option that I've also used in the past is simply to invite to the Minecraft game from the Friends List. Once your friend is in their game and has it running, they can try sending you a Game Invite from your profile on the Friend List. That should
work as well. Good luck!

Can any on my friend list who have Minecraft join my existing game when I designate it "online" as opposed to invite only? With that new "friends of friends" option I should be seeing at least one game at all times but so far zippo!

Hey there CompactedMatt!

If you're looking to get an invite to be in the Preview Program, you have a few options. You're on the right track of needing an invite from a friend, however I would suggest either asking those on your Xbox Live friends list who are currently participating
in the Preview Program to get an invite or head on over to our Xbox One General Discussion forum, make some friends in there who are participating, and request an invite from them.

If you have any Xbox Support related questions in the future, please feel encouraged to create a new thread here on the support forums. We're here to help!

Hey there DaGangstarGTG,

We are unable to provide invites to the Preview Program, as you can only receive an invite from someone who is already currently participating in the program. When you have a chance, I would suggest reaching out to a friend who is currently in the Preview
Program and request an invite from them. Another option could be heading over to our Xbox One General Discussion forum, make a few friends in there who are in the preview program, and ask about getting an invite. Thanks!