There is someone else's illustration in it there is a certain effect that I don’t understand how it was done?

Question

Vector graphics

I bought an image, and I want to repeat the effects applicable in this image and I don’t understand how it’s done, experts, please tell me. When I create a gradient fill, then in my layers the object is a rectangle, and in this work it is a contour. That is, I do everything the same, but the object remains a "rectangle" and when I create a clipping mask and save it, when I open it again, the eps file is transformed into a raster for some reason. How can I make my layers have an outline and not a rectangle?

Answer 1

Nothing happens, after saving eps turns into a raster.