Hi....yes it is possible.
Sure. You can just project geometry you want on to the imported STEP file.
Is there any problem you encountered?
How did you import the STEP?
as composite surface?
More information is needed.
Can you attach the STEP and resulting *.ipt here?
You can edit any surface or solid geometry in Inventor.
You didn't answer any of the questions above.
Attach your STEP file here.
Asking the same question multiple times will not likely result in different answers.
You can also Unstitch a solid into surfaces, but I suspect you will need to provide more information.
i am aware of the procedure. Please answer the question if you have the answer. I already know how to do this. I just want to know why some files can use just surface while others use solid.
I think it is depended on the original STEP file contents, you know that STEP format is a neutral format and can generated by many CAD software (i.e. Inventor, SolidWorks, NX, ProE, CATIA......), so if the original model designed in CAD software has only solid geometry then the exported STEP file will also has only solid information and also only solid can be imported into Inventor, vice-versa for surface geometry.
Correct me if I am mis-understanding your question.
Quality Assurance Team