1)New cluster is 6.5, old one is 5.5. Both connected to vcenter 6.5
2) Not sure ? After ~8 hours the "Recent tasks" changed it's status to match "tasks & events" (cancel requested), and after 24hours it's still at the same state.
3) see 2
4) see 2
So I'm not quite sure, if it's migrating, cancelling or cancelled.