IS IT POSSIBLE IN CREO TO MANIPULATE THE BASIC SKETCH FROM A IGES OR STEP FILE IMPORTED FROM OTHER SOFTWARES LIKE CATIA OR SOLIDWORKS .
PLEASE TURN OFF THE CAPS LOCK!!! WE HEAR YOU!
You can open a DXF file directly into a sketch. Use the Open dialog and filter for DXF. When you selected the DXF file, you can open it as a sketch.
IGES and STP files are not 2D curves, typically. They will try to open as parts or assemblies with any sections or sketches. If you do have curve geometry, you can project them into a sketch. This is a copy operation, but not a direct manipulation.