Do my roll-over nights begin at 40 if I've stayed at 4 brands? What would happen in the following scenarios?

1.
40 nights + 4 brands by April 2014
40 more nights by Dec 2014

2.
55 nights + 3 brands by April 2014
25 more nights + 1 more brand by Dec 2014

3.
70 nights + 3 brands by June 2014
30 more nights + 1 more brand by Dec 2014


Also, if one starts with 36 rolled-over nights in 2015, will 4 nights with 4 brands re-qualify platinum until end 2016? (I can't see why it wouldn't)

Lastly, if I begin 2015 with 60 rolled-over nights, do all of my nights in 2015 immediately become roll-overs for 2016?