Looks like a monstrose form of Cereus forbesii. No, it will not end up looking flat, fan-shaped. Change the soil to something better draining & water when dry. Watch out for snails. They like to eat it. :P I have never seen mine flower, but then, the snails got to it, deforming it badly. I have read that this one does flower.

I shouldn't think snails will be a problem unless mushibu10 has indoor gastropods. This plant won't live outdoors here.

thank you both, and it is inside no risk of snails! what soil would you recommend?