Can the 5D Mark 2 work? Is so, what cable is required and will the functions work as the 5D Mark 3? Also will there be future updates for the 5D Mark 2?

We have just replied to your another thread: https://forum.dji.com/thread-213515-1-1.html  
The weight is less than 3.6KG, the camera width does not exceed 205 mm, and the height does not exceed 150 mm. The Ronin-S can normally provide stabilizing functions. Some models of cameras may not be able to use Ronin-S control functions. Canon 5D Mark II is not in the list, the control functions cannot be ensured and we do not have the cable to recommend. Hope other users who have the same camera could give you some advice.