you do a speedrun of the single player part but you alternate between players throughout the different chapters. same rules that apply to the normal single player speedrun but the 2 players split the chapters 4:5 and they can do what ever ones they want

no

while its an interesting idea, it wouldnt really fit on the main page, however if you want to record a run of it that would be the best way to potentially get it to be a category on the category extension side