Yes, (mostly) but IF … IF you use the open model in a read only way. The C API is not a “live” API that can modify the active model object. Doing so may crash SketchUp and/or corrupt the model.
In your other post, I pointed you to a rudimentary example by the Extensibility Team that they posted on GitHub.
Be aware that here still are features that have not yet been implemented into the C API. You can browse the API issue tracker using filters to see what has been asked for and logged already …
In your other post I asked you to tell us what kind of experience you have with C and Ruby.
How much do you understand about the SKP document object model and how the SketchUp application works ?
We need to fix your starting point. (That said, a forum isn’t the best means of education, but we can point you too other means, and help you solve problems when you get stuck.)