I agree that abc export and Houdini Engine is not an option in Houdini Apprentice, but you won't miss much with those limitations. I had the same impression about the complexity of Houdini when I started and twice gave up on it. At this point, I actually find it much easier than dealing with the frustrations of the limitations of other programs.
But if you want to solve your issue with moving something from Houdini to C4D, don't start with a vellum node. If you knew Blender and had never used C4D and tried to jump into a file that had a lot of Xpresso code and mograph, it would look a little intimidating. Instead, add a cube/box to Houdini, double click the node to get into geometry mode, (not scene mode) select a couple faces and add a polyextrude node and increase the "distance" setting from 0 to some small number. Then right click the polyextrude node and select "Save". Name it "test.obj" and make sure you select a directory you can find. Then see if you can import this into C4D. If you can, then try something a bit more complex, remembering that Houdini (and a few other programs like Modo) can render points or curves. These will not render in C4D, which needs some sort of polygon surface.
FWIW, right clicking the first node (box) and selecting "save" will export a cube object. Right clicking the second node (the polyextrude) and selecting "save" will allow you to export an extruded cube object. You can also click the right edge of each node icon to go through the steps of building the model. That is essential for learning Houdini.
When I used C4D, I often kind of - sort of understood 3D modeling. Houdini is not kind, when that is the case. For example, you can add a sphere in C4D and then click render, and it will render a sphere. Currently, Houdini is pretty good at filling in the steps you didn't do in recent versions, but in previous versions, unless you also added a material and UV maps and a light and a camera (to use for rendering) and a render node to specify settings - it would sometimes crash or give weird results. C4D generally gives you a UV map by default. Houdini generally doesn't. I think these are some of the reasons people find Houdini hard to learn. In the end, it may not be fun for you to work in Houdini, but adding Xpresso or Mel code or whatever to fix limitations or buying numerous plugins can be even more difficult. I found that in C4D and Modo that the Nurbs or procedural options only got me so far and most models required that I make these editable polygon meshes. At that point, one couldn't go back and tweak earlier steps. There is no such limitation in Houdini.
Here is a quick video of how to move something simple from Houdini into C4D:
StartHere.hiplc