GMAT In-Person v. Online

Super confused about how this works. Is the in-person exam paper/pencil with Scantron like the ACT/SAT or is it online? Are both adaptive? How tf does that work?

If you get a question wrong, edit it and make it right, do you still lose points? That sounds stupid

I took the GMAT official practice test (mba.com) and got a 84 verbal (15/21) , 87 qr (19/21), and 88 di (20/21). These were separate sections as I did them one at a time, but am I crazy for thinking 770+ is possible.

Thank you!