GS Mobility Across Classics Offices/Groups

How difficult is it to move across classics groups/offices from SA to FT? Is it viable to switch group and office (ie. Houston NR to SF TMT)? In other threads, people alluded to GS being less supportive of switching groups with some saying that your return offer in your existing group may be pulled if you apply for mobility

Also, what does the mobility process entail? Do you apply for a FT role that's posted and go through the same process as lateral hires (hirevue, superday), or do you skip the hirevue and just interview with the group you're interested in?