You will "automatically" be in Open Mode whenever you install an Open Mode kernel. (so if you ever have loaded a non-Nokia-signed kernel, only for a split second, for example to boot into rescue mode, you already are in Open MOde) The thing is, there are different kinds of Open Modes If you enter open mode accidentally/unprepared, there is just a load of problems you might encounter, and you need to apply a number of fixes. If you do it the recommended way, you just get to the same point but with less tweaking needed.