11806
1. Is "old Anakin" part of the normal Vader figure or is it a chase as well?
Yes, the "old" Anakin Head is the standard figure. The Luke Head w/Damaged Mask is the Chase.
2. Is it possible to get Luke and Han variants in the same box or is one limited to HK?
Neither is limited to HK or Japan, they have both been found in both places. What is different between the HK and Japan Master Cases is the placement of the Chase figures (apparently).
It is NOT possible to get BOTH Han and Luke in one box of 12. You get 2 Han Stormtrooper -or- 2 Luke Stormtrooper in that particular box, no one has found chase box with one of each.