hi, I would like to use two different presets, one on Part A and one on Part B, and change them as I wish, is it possible?
If I understand you correctly, than no, this is not easily possible.
For the Rev2, a Patch is always two layers, and multi mode allows you to play the two layers independently on two different MIDI channels, think of a split with a second keyboard playing the other layer.
But a program change message for a layer alone doesn't make sense, as a patch is always both layers.
You can create new patches with a different combination of A and B layers, and so make all combinations you want possible.