I have an s3 with cyanogenmod 13 (Android 6.01). Went to the app store today to find out s3 is incompatible even running v6.01. Installed the apk from apkmirror and that works fine.
phone in pocket and using the Go+
but I have used these and it's difficult to spin the ball
use this on my bicycle
https://www.amazon.co.uk/gp/product/B01IVGXHMC/
and I also have this case
i have this beast
https://www.amazon.co.uk/gp/product/B016DA61V2/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1
keep my phone + like 3 friends phones fully charged all day no problem with charge to spare.
I've found that the seal can sometimes be fiddly to secure...
and I also use this for rainy days (it has an audio pass out cable)
Yes, my AR doesn't work either, and it's because my phone doesn't have a gyrascope. Battery saving mode doesn't work either because of it.
Install the app sensor box to check what sensors your phone has.
go to the google play store in a browser and sign in with the gmail tied to the phone, on the pokemon go page when you click install it should list your devices and either say incompatible or not available in your country like so: http://i.imgur.com/LYpi4mM.png
link to the play store page: https://play.google.com/store/apps/details?id=com.nianticlabs.pokemongo