If you ask around about viva length, two to three hours is fairly common. If you google you’ll find lots of lists of standard questions. On the day you will probably find out the result within thirty minutes of the end. (and you’ll probably get minor corrections)
There are broad expectations for the format and tone of the viva. But you can also expect that yours will be unlike anyone elses. My viva was four hours long and I was stood for the entire viva in front of a blackboard. I didn’t expect that and I don’t expect it for your viva! I started stood up giving a short presentation, and things just went from there.
Ask your friends who have had vivas recently what they were like. See if there are common experiences but know that yours will be a custom experience to examine you and your work.