How to split multipiece core/cavity?

I WANTS TO SPILIT TWO OR ONE VOLUME IN A WORKPIECE. CAN ANYBODY TELL ME ABOUT SHELLHOUTTE CURVE AND ITS OOPTIONS HOW TO MODIFY THIS CURVE AFTER DEFAULT CREATION (LIKE LOOP SELECTION, SLIDES.GAP CLOSURE AND DIRECTIONS .. PLZ SIR TELL ME HURRY . BCZ. I HAD FACE MANY TIME THIS PROBLEM IN INTERVIEW OFTEN.. PLEEEEEZ.