Can the ZTE Axon Pro handle multitasking?

If I play music on my LG G3 and try to do something else, it starts getting slow. Not the kind of performance I would expect for four hundred bucks.

On Newegg, it looks like you have control of the aperture, and it goes down to 1.0. How can a cellphone for $449 have an aperture of 1.0?

And it looks like a Olympus 17mm f1.8 lens is cheaper then that phone. My f2.8 is good enough, don’t use camera anyways.