This ROM is based off android 6.0 then ported to the nexus 7 2012Kid, even if it would be that case, the app "android system"'s version would be 6.0. You just built android 5, and setting its version code to 6.0 and adding the new boot animation in 2nd zip. Also, in build.prop, you have api version 21 and build fingerprint is also LRX21P / 5.0. Don't think I'm an idiot.
Or tell me why all those features aren't working in your ROM, but in real Marshmallow port by dmitrygr they do work.
IF you are going to stay here and be annoying then you can leave
Their are 5+ people who have tested the ROM and found it fast, stable and based
Off android 6.0
Also some of the features are not working because of hardware requirements and the
Multi window is their but does not appear because of a bug and that will get fixed in the next update .