Is nature's bounty multi vitamins safe to use?

Depends. Many multivitamins have too much iron and copper in them. Copper and zinc should be in balance, and are competitively absorbed. Many people already have enough copper and insufficient zinc, therefore a supplement with copper is often undesired. Iron can be an oxidative stress on the body, and we do not supplement it unless clearly needed. So read the label to decide.
Yes. I have taken them before without a problem. The only caveat is if you are pregnant. It may have a higher dose of vitamin a than is good for a baby.