Distance is separated in space or time.
Proper length in physics is the invariant measure of a distance between to separated events. It is considered as the ideal length in a space-time of space-like paths.
no, it can not be separated by a physical process.
Space-time is a concept used to describe a medium that extends throughout the universe. It helps explain how gravity bends light around large objects, as an object is said to warp space-time and therefore creates a distortion which light follows.
When two or more waves occupy the same space at the same time, an interference pattern is created.
The space-time continuum is a complicated concept.