Could be by: Jacki Cammidge, Certified Horticulturist
This looks like Austrocylindropuntia subulata, but it's in real need of more light. These are high light plants, like most cactus. But don't just put it in direct sunlight now, after it's been deprived, because that will kill it.
More on how to grow it; https://www.growplants.org/growing/austrocylindropuntia-subulata
And lots of detailed information on it; https://www.cabi.org/isc/datasheet/115976