"18 Pro On Us" question

Are the trade-in deal and the new line deal the same promotion or can I do 4 deals of each? More specifically I am asking about the "Max 4 discounted devices/account" verbiage. Can I add port in 4 lines to take advantage of the deal without trade-in and can I also trade-in on 4 current lines for a total of 8 new phones? Or is my whole account limited to only 4 promotional eips at a time?