Question

Is it possible to compile program on one platform and link with other ? What does object file contain ? Can we delink an executable to produce object file ?

Answer 1

No. In general object file formats might be the same, e.g. ELF, but the contents of the object files will vary from system to system.

An object file contains stuff like:

Object code that implements the desired functionality
A symbol table that can be used to resolve references
Relocation information to allow the linker to locate the object code in memory
Debugging information

The object code is usually not only processor specific, but also OS specific if, for example, it contains system calls.

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Edit:

Is it possible to compile program on one platform and link with other ?

Absolutely. If you use a cross-compiler. This compiler specifically targets a platform and generates object files (and programs) that are compatible with the target platform. So you can use an X86 Linux system, for example, to make programs for a powerpc or ARM based system using the appropriate cross compiler. I do it here.