From Designer Jack Radey, 5.10.2002:

1. Can German Divisions and Soviet Corps be switched (i.e. reattached)
between different Armies and Groups at leisure, or is there any
restraint? Are they reattached at the start of the turn? 

No restraint, at the start of the turn is correct. 

2. On what column of the German Command Track should the SS Corps and
Division Formation markers be placed? 

I don't remember, check the historical commentary. Whichever army
commands the Kharkov region commands Liebstandarte and Das Reich, I
believe they are under the SS Corps HQ at that time or shortly
thereafter. 

3. Can SS Divisions be reassigned to Wehrmacht Corps or Armies, and
viceversa? 

Yes. And were historically. 

4. What's the place of German HQs like Cramer, III, XL, XLVII, LVI in
the command hierarchy? 

Subordinate to armies, commanding divisions. 

5. Can they, once deployed on the Command Track, be reassigned at
leisure amongst the different German armies? 

Yes, and were historically.