If I need to create a dimension for the yellow hole. Do I need to give the dimension from the edge ( where green and red faces meet) to the center of the hole in a 120° angle ( which the hole is created or
I have to give the dimension from the edge to a point that hole will project on the plane3 ( parallel to the red surface)?
If I have to the second option , how can I create that ( easiest way)
The way the image in the part shows is dimensioned from the edge where the red and green faces meet. So you could do it the exact same way. I would not recommend projecting the hole out to the red face.