After installing Interaction Hub 9.1, do both the Jun/Jul 2015 and the Feb(?) 2016 images need to be

We implemented Hub with Tools 8.55.02.  We really have a couple of questions:

1.  Would going to a "new" image (it will be the first time we utilize the imaging / PUM world) automatically include a Tools patching or is that done separately (manually)?

2.  There is an impression here that since the mid-2015 image enables selective adoption (?) we have to process it before the early 2016 image.  It seems to me that the 2016 image would be cumulative so it could be processed without the 2015 image being done first, and that in doing so there would be no loss of functionality.  Which is correct?

Thanks for your help.