The merger was 7/8/08, years after character transfer from mid 2006.

[4] “The precursors to modern-day heirlooms were introduced in Vanilla/Classic World of Warcraft. Heirlooms up to the Wrath of the Lich King expansion were items that were sold by a specific battleground vendor. There were Warsong Gulch, Arathi Basin and Alterac Valley heirlooms.”

[2] This depends on how you mark an expansion. IMO, after the initial bug fixes are put that’s the expansion. Everything after that like 3.3.0 is it’s own separate patch.