There are differences between people, who can benefit from B12.

I think in your case, having a tentative diagnosis of autoimmune disease...3 months of very high dose steroids, the hyperbaric oxygen treatment, etc,
your needs are probably (no guarantee) for remyelination of damaged nerves.

You are very young to have failure of intrinsic factor. But it can happen.
If you were totally vegan before you became ill? Or if you used acid blocking drugs to protect your stomach during that long haul with Prednisone.

Here is an article that suggests Omega-3 for damage to the nervous system.
http://www.sciencedirect.com/science...bdd1ed86239c46

In order for the Omega-3s to work you do need the 3 Bs... B12, folic acid and
B6. So if you want to try and get that pain out of your legs...I'd give this a try. It takes months to repair, and you won't see sudden results.

There are going to be people here reading this forum, who have hereditary errors in B12/homocysteine chemistries. There are going to be people with malabsorption from disease (like Crohn's), or damage from chemotherapy, or chronic damage from lack of stomach acid, or destruction of the cells that make intrinsic factor.

You can also try to increase you food consumption of antioxidants, like that article suggests. Red, yellow, orange, purple fruits and veggies are high in these.
Broccoli is very good too.

You are young, and I think you can heal. But healing takes time, and some effort on your part.