Let's deal with one, first.
Let's say you sent out bits to turn on #1. You clock out 0000 0001.
Later you want to turn #5 on and leave #1 on. You clock out 0001 0001.
Later you want to turn off #1 and leave #5 on. You clock out 0001 0000.
Finally, you want to turn on #4 and #6 and everything else off. You clock out 00101000
You have to send/re-send the whole stream each time. See?