The Epcot line runs between the TTC (Transportation & Ticket Center) and Epcot.
The Express line stops only at the TTC & MK.
The Resort line stops at the TTC, Polynesian, Grand Floridian, MK, Contemporary.
There are buses between all parks, except between MK & Epcot. So from MK or Epcot to Studios or AK, you would simply take the bus -- no monorail involved. There are also buses from all Monorail Resorts to Studios & AK.
From Epcot to Studios, you can also exit Epcot at the International Gateway, between UK & France, and take either a boat or the Skyliner aerial lift to Studios, or you can walk about a mile and a quarter. You cannot transfer between the Monorail and the boats or Skyliner without walking thru Epcot, which requires admission.