Can I Give My Cat generic methyl/cyanocobalamin?

Yes, with care
Vitamin B12 (oral cobalamin) is commonly referenced for cats at published doses. Published guidance for cats: 250 mcg per cat, every 24h. Same caveat: injections are standard for low-B12 cats.
Source: Veterinary Partner (VIN)
Get the exact range for your cat's weight

The safe habit

Confirm any medication decision with your veterinarian, who knows your cat's health history and other medications. VetDose shows published reference data, not prescriptions.