Hi Josh! Nice to see you here. :o
Its absolutely ok if we do not have UE4 rendering features on, for example, adreno 200.
All we can ask for low-tier devices is low-poly LDR, 2D funtionality and all non-gpu features. In other words, UE4 for low-tier can be more gameplay framework than rendering engine, and it will be pretty enough (in my opinion). 
From that position you can just go forward with new devices and dont waste your time for deprecated ones, as long as we can run at least Tappy_Chicken-like applications (and question of this thread is: “We actually can run them on deprecated hardware and os versions? Minimum requirements for this?”).
Thanks for your attention to our questions! :o