Microsoft is a kernel contributor, and Android isn't really linux
Qualcomm's contribution to the Linux kernel, is, AFAIK, limited to software that make Linux run better with Qualcomm SoC. So, they are not really improving Linux - they are using it as a bait for you to run your Linux workloads on your Qualcomm phones, using Qualcomm's hardware technology.
No, not really.
To make it easier though I can point you in direction of Alan Cox commits around 2010-2013 and his work on TTY subsystem in particular.
Do you see RMS's point now?
To the extent that Linux implies "GNU Linux", i.e. a whole operating system and a broadly interoperable and source compatible set of *nix services, Android is not Linux any more than iOS is FreeBSD.
RMS believes that userland makes an OS, because he wrote a userland. Linus believes that kernel makes an OS, because he wrote a kernel. Calling Android "Linux" is like calling Windows 8 "Windows NT", i.e. correct if you're talking about kernels and wrong otherwise.