Yes, some teas contain nicotine, but not the usual ones you find in the supermarket, potatoes, tomatoes, red peppers and some mushrooms also contain nicotine.
Yes some do I found this out on google.com
Yes but not absolute form which is not harmful to human body.
Most of it is very positive. However, foods and drinks generally contain many complex chemical compounds, not all of them "good for you." Nicotine is an addictive substance found in tobacco, eggplants, potatoes, cauliflower, and, according to one study, tea.
Some teas contain caffeine, I don't know of any that contain nicotine but I guess it wouldn't hurt to read the labels.