Is baking soda safe to you on teeth to whiten?

Yes. It has been used as a dentifrice for years. Caution with any abrasive and excess scrubbing but it should be fine to use to remove extrinsic stain. It won't change the internal tooth shade, however, so it may or may not actually cause your teeth to look whiter.
Yes. Baking soda can be used as a whitening agent. It is important to use a Fluoride toothpaste though. You may want to look for a toothpaste that has both whitening and cavity protection.