In part 2, we take the same position and idea, but up the ante considerably.
Now we are dealing with 2 fingers, moving in pairs, while the others remain anchored on the G-string.
Now it is important to note that even though you do not HAVE to move one finger back to the G-string when ascending in order to have the correct notes ring out, you SHOULD, from a practise stand point. Descending though, you definitely have to move them back to position. In "real life chording" you might even hold some fingers off the fretboard instead, depending on the progression.
As with part 1, take a look at the video, since this exercise is easier understood by viewing the example than trying to read about it in text.