1) Yes, as long as you have the appropriate LabVIEW development environment for the other OS and you aren't relying on platform-specific features such as ActiveX. Any CIN's/DLL's that aren't part of LabVIEW would obviously also need recompiling.
2) No, unless you can get it to work under some kind of emulator like SoftWindows on the Mac. To build an executable for a particular platform you need the LabVIEW development environment and Application Builder for that platform. Maybe someone else can help with the Linux and Embedded XP questions...
