this is my new fairy castle cactus also referred to as a green finger cactus(https://i.stack.imgur.com/ZpBSg.jpg)
Try to ask in the seller, sometimes they know.– bennJun 12, 2019 at 10:08
I bought it from Walmart and they said they have no idea...– ChelseaJun 12, 2019 at 12:58
It's virtually impossible to get an exact age. From the way these look they may be rooted cuttings which further obscures things.
Grown from seed, I would expect a plant like this to take 2-5 years depending on conditions.