I’m flying a multi city single day itinerary tomorrow (7 segments), when I try to check in on the AC app it will only let me check in for the first part of that itinerary. At the airport can an AC associate check me in for all 7 legs at the same time and print all my boarding passes?

also, if my last 2-3 segments are in Business Class, will that allow me to board earlier on all my earlier segments / use MLL?