Universities have regulations about thesis examination, conditions that they expect. But every viva will be different from every other. Every PhD thesis and every PhD researcher is different from every other. Your viva won’t be like mine: it’ll have the same goals perhaps, but it will be different.
Every snowflake is different from every other, but we know how to prepare for a blizzard. Your viva is going to be unique, but you can still be ready for the day it comes. Plan a little, prepare a little and you’ll be fine. You’ve come a long way already.