iOS Autolayout: Handling different screen heights

I am desperatly trying to get to grips with Autolayout and need advice on how best to approach handling the following scenario. I am working with an existing design that I need to lay out appropriately so it will function on any iPhone screen size.

For each screen, I have identified a section of the app that should partially expand/collapse to compensate for the difference in screen height. I have illustrated this in the image below. Primarily, is this the best way to approach the problem?

Assuming this is the best way to approach the problem, how should constraints be added to fix the positioning and heights of views 1,2 & 4, while allowing view 2 and it's content to flex in accordance with the device view height?

I have experimented profusely with constraits and have been unable to achieve the illustrated outcome.