Questions about vision position! Time for an FAQ

Hey,

i am a little bit confused about the vision position topic. The dev wiki is not well documented for somebody who wants to get in to it.

  1. What are the requirements for vision pose init? When is it set?
  2. How is the beta fault calculated? → i need a documentation about when it will compare rotations etc. A lot of things are not self-explaining.
  3. Why is Hold/Auto.Hold/PositionHold Mode rejected. Vision Position is ok, but flightmode is rejected. Offboard works with setpoints. → a lot of time to find out that only offboard works
  4. Is an auto.takeoff possible without local position (just with baro). → is a vision init in air wanted? or do i get it actually because of randomness? that how it feels without a good understanding what happens under the hood

thanks for any help!