Yes, curd and all other dairy products have vitamin B12.
It depends whether you are having specifically B12 deficiency or any other disease. If you are having B12 deficiency then you are recommended to take B12.
No, there is no evidence that consuming water along with B12 will help pass the THC test.
All kinds of meat and poultry food items are high in vitamin B6 , B1& B12. Fish (tuna) and salmon are also rich in vitamin B12 and vitamin D.
Doctors do recommend a B12 test to evaluate B 12 deficiency