© Jeffrey J Wolynski

Concerning the differential rotation,

Differential rotation is Marklund convection. We have what is called "wind" on the surface of the Earth (Black dwarf star). It does not mean the rocks below move with the same velocity, or even move at all.

The iron shell of the Sun could be mostly static (immoble). Plus it could give structure to the material in the outer layers similar to an insect's exo-skeleton. Thus leading the Sun to resemble a perfect sphere, hollow and highly organized in the surface only. 

I don't know if this will be moved and placed back in the stellar metamorphosis catagory but it is duely noted ALL stars will exhibit differential rotation as they are incubating the "planet" in their centers. 

http://astronomyonline.org/solarsystem/Images/GasGiantInteriors_th.jpg

http://www.noao.edu/education/gsmtf/img/winds.gif

 

Differential rotation is inferred from helioseismology