Does mvi (multivitamin) hava all vitamins in it and enough vitamin b?

Depends!: The answer to your question depends upon which MVI (multivitamin) to which you are referring. They're all different so you'll need to read the labels. The more difficult question to answer is how much is enough b vitamins. There's the rda or something like that. It's based upon minimum amount to prevent disease rather than amount necessary for optimal health. So the answer remains controversial.