I dont get the obesession with the cube, if iam not entirely mistaken, you cant open it anyways yet. It will need some episodes more. I solved part II but thats it, and nothing came out of it. So... the cube is pointless for now. And yes you can start it anytime, not only in the first free roam, so we will be able to use it in future episodes to from scratch and solve it if its done by DPC. So far it has no use...can someone describe it a ilttle bit more?
But to make it clear what is meant by step 2.
You push the button in the center, and you see symbols disapear. Its always the same pattern, push it through and you will notice 4 symbols that NEVER disapear. Those symbols you have to put in I and push the button in I again to solve the second step... But than it doesnt go on and you dont get anything for solving step 2 either.