Also, I've heard you can get high from secondhand marijuana smoke. Is this true?
Oh god yes. The smoke still contains THC even after it's been through someone's lungs, so if you're present at a clambake, you can (and most likely will) get high just from breathing the smoke. As for breathing someone's smoke as you walk down the street, no, not so much. There's not enough THC to get you high unless you're breathing secondhand for an extended period of time.
I do gummy bear vitamins every day. They are legal and you can get them at pretty much any store with a pharmacy. I take usually 2-3 a day, anything more is supposedly not safe and you can OD.
You can't OD on vitamins, your body just flushes out unused vitamins. Too much can cause painful buildups though.