Answer 1

In hope these help:
A C++ object file is an intermediate fileproduced by a C++ compiler from aC++ implementation file and the C++header files that the implementationfile includes. The C++ linker produces the output executable or library of your project from your C++ object files.
http://docwiki.embarcadero.com/RADStudio/Tokyo/en/C%2B%2B_Object_File_(*.obj,_*.o)
https://stackoverflow.com/questions/8249945/what-is-object-in-object-file-and-why-is-it-called-this-way