Hi
@MSBuddy25Focus mode is when someone is sharing a PowerPoint presentation - this will hide everyone's camera stream at the bottom of the meeting stage so everyone can concentrate on what's being shared in the meeting as opposed to being distracted by the streams.
You can maximise the meeting in the top right of the pop-out. In terms of full screen AFAIK it's not possible currently through the new meeting experience. You can see a lot of comments here on this uservoice
https://microsoftteams.uservoice.com/forums/555103-public/suggestions/35708995-show-meeting-full-scr...Of course this has probably occurred because a lot of people also complained about a floating controls bar which made Microsoft put the controls in the top of the meeting pop out. So if you want to see this back in, vote on the uservoice. I think there should be an option personally as it is now, but go to full screen and transition to floating control bar like previously. Best of both worlds
Hope this answers your question
Best, Chris