There are two generations of difference between the two, different SoC, different GPU, changes that they bring and some can't be backported since they are hardware related. Where something is supported in new version, may not work in previous and vice versa what is known to work on old device may be patched, disabled or otherwise modified on new either for compatibility, security, UI bugs or other purpose. I would not expect the same app run on two different devices in exactly same way.