Ok, so promo tickets allow changes. So, a hypothetical question. If one has booked a one-way promo award in economy for travel after July 1 (paying e.g., 17K miles), can that subsequently be "changed" to a one-way business class promo (for 40K miles), while paying the difference (40K - 17K = 23K miles)? Or, are changes for promo awards ONLY allowed in the same class as in economy to economy?

Second independent question :
Can changes be made to the promo ticket for the origin and destination?

Thanks