I'm not sure when the promo started, but according to the terms&conditions, the tracking period is between 1th of march to 30 april.

Even though I suspect that the offer has been marketed in the scandinavian countries only (?), it is open to members in most non-scandinavian western european countries as well...

Connecting flights to LHR are included, at least from Scandinavia. About other countries, I don't know...

Surf to the BA website, select a scandinavian country in the "worldwide" menu, and voila: you will have a banner with the offer.

www.british-airways.com/regional/sweden/

About D-class: I haven't got a clue...