This looks like a Euphorbia, not a cactus, not Acanthocereus tetragonus. I would like to propose moving the image to the genus listing for Euphorbia unless someone else can identify the species.
You will get the best answers to your questions if you ask them on the Ask a Question forum or the Cactus & Succulents forum:
https://garden.org/forums/view...
https://garden.org/forums/view...
Any ideas about the ID, folks?
