first of all , sorry for my english....

i am at act 2 last boss .
my friend want to play with me ,so we start game together tonight ,he is finish the story mode before.
when we start the game (i host ) i find we are at act 3 the end ,and i can not go back to act 2 .even i quit the team and start by myself ... still at the end of act3.....
can i do sth to play my own online save point at act 2?
plz , thx for all