Nearly all correct. As the local airflow speeds up over the wing it will eventualy reach M1.0, and a shockwave will form. It should then run back to the trailing edge, but because the shock is still weak, the high pressure behind the shock keeps it at about 50-60% chord while the aircraft goes faster. When the shock gets big enought it finally and suddenly moves off to the trailing edge.
The bottom shock forms and goes straight back in one movement. The difference is because the aircraft is producing lift, has a positive angle of attack and a greater flow over the top surface.
Not much difference between the shockwave angle and the Mach cone angle except that away from the aircraft the wave is less intense.
Dick W