It should, yes. We don’t tend to count “who purchased” as a qualifying factor. The promotions look at if you have the license on your account or not.
Aye, that part is primarily if you have it on another platform (console, Steam, etc…). If you have the license on your Battle.net account you shouldn’t need to log into Diablo.
I’m fairly certain this is how it will work, but I’ve made an inquiry and will update the thread when I hear back.