It depends. If you use the NDK you have to make sure you can build for both x86 and ARM (the play store will hand out the relevant variant silently).
Also, Google have done some serious work to ensure at least some backwards compatibility (and providing a support library, that i fail to recall the exact name of, for backporting various functionality).
While the FOSS world seems to lean on "compile it" along with "lacking resources" as an excuse for not maintaining anything more than incidental compatibility across releases.