It definitely could, I'm not a doctor so I don't know for sure how everything works, but I know nicotine affects your brain and can definitely affect your mood, attention, and impulse control which could counteract medication. It's a brain altering chemical so it would make sense that it could change the way your medication would work. Quitting vaping/smoking is always easier said than done but it might be a smart idea, or at least trying to cut back. But again, that's easier said than done.

Vaping what? I doubt a tobacco vape would have a noticeable impact on your meds but there is a greater likelihood that THC vapes could have an impact, but of course you should talk to your doctor about it.

it all depends on the medications and doses i believe, but it definitely can. bring it up to a doctor or psychiatrist.