In my module/subsystem, trimmed down version of core data processing of the parent system will be used ONLY so which one (option 1/2/3) is correct?
[The Core Data Processing is the real and complete business case but the subsystem, to which this diagram belongs, will not use this complete scenario but just some parts of it]

Option 2 and 3 are both correct. I haven’t seen option 1 before.
If you only use Core Data Processing in one place, I wouldn’t bother extending it. That is, use option 3 if you don’t reuse Core Data Processing in more than one place, otherwise use option 2.
Usually you want your use case diagrams to be as simple as possible, so avoid specifying too much. Do you really need to specify Core Data Processing in this use case? If you think it’s important at this level, then include it. Otherwise, just stick with the simplest diagram that gets the message across.