Looks rather sad and diseased. Maybe that’s fungus growing on it, can’t quite tell from the pics, can you get a real good close up? Could be mealies maybe? Also it’s tightly potted, maybe repot in better mix/pot and treat for whatever the white stuff is...when it’s been ID’d properly. Yes it’s etiolated/light starved, that’s why growths are weak and not self supporting.

I would get some fungicide spray and spray it outside

Powdery mildew, maybe?

Scale. I have a large screen so i can see a dark core surrounded by a white circle .Ive had it, and this is a really sever infestation. Spray it with insecticide, and clean it very thoroughly.

If you act fast, you can get rid of it. Ive lost 2 plants to this, but 2 recovered....

I'm thinking scale also. I had to toss a Mammillaria that had the same thing since I just couldn't get rid of it. :(

Edit: If this was my plant I'd get rid of the two most infected arms and spot treat the others.