About 64-bit Android on Tegra-X2

Android is not officially supported, but you will probably find an Android port. I couldn’t answer the 32/64-bit question, but the ARM Cortex-A57 supports both a native 64-bit mode and armhf 32-bit compatibility mode (I wouldn’t expect great performance). Usually the case of whether you can execute both 64-bit and 32-bit is if the 32-bit linker and support of 32-bit libraries are present. In the default case of the L4T which comes with a JTX2 only 64-bit support is natively installed (this isn’t Android); adding foreign architecture of armhf could make that o/s compatible with both 64-bit and 32-bit simultaneously.