How do you create an 8 bar melody using one reference note and then changing pitch and stretching the time?
We would need more information to help you with this. Are you talking about recording one note in Audio and then manipulating it? Or are you referring to using MIDI to create the sound? What is the reason for the time strech (slow down, speed up, beat match, etc)?
Please note that LE6 is our entry level OEM product and does not have all of the features of the flagship Cubase 7.5, so some processing options are not available there. You may want to consider 7.5 for more advanced features.