Is it possible to change the speed and limit the rotation of a motor?

If you mean the Motor surface type then yes, quite easily. the second-to-bottom block of properties for Parts is called Surface Inputs I believe. That's what it is and that's what it's for; you simply find the corresponding surface of the part that has the Motor, and change that surface's SurfaceInput property to Constant, and tweak its ParamB property to change its speed. I'm not entirely sure what the ParamA property is for, but I wonder if it controls the power of the motor, though it's more likely that it simply does nothing (yet).