Will 32-bit native code work with a 64-bit VM in Java?

No.  All native binary code that was written for a 32-bit VM must be recompiled for use in a 64-bit VM.  All currently supported operating systems do not allow the mixing of 32 and 64-bit binaries or libraries within a single process.  You can run a 32-bit Java process on the same system as a 64-bit Java process but you cannot mix 32 and 64-bit native libraries.