Could you clarify for reference the IP status of original work I might place on an Instagram or Facebook page?

If the work you place on social media is an original work and you produced the image (for example) yourself, it will have copyright protection belonging to you. However, to assert your ownership you can use the copyright symbol of c in a circle, plus your name and date. You can also lodge it in the ACID IP databank for extra evidence should you need it.