Until old-age. Adult teeth continue to grow, but very very slowly. Normal chewing/grinding help to keep the teeth at appropriate length. An unapposed tooth can grow long to cause problem. Excessive grinding, more often during sleep, will wear out the teeth earlier...But your teeth probably don't stop growing until old-age. Healthy teeth=healthier body/heart. See dentist regularly. Good luck.
No. The roots of the teeth are not fully formed when the tooth erupts into the mouth. 2-3 years for complete sealing of the roots.
Teens-Early 20's. Wisdom teeth are the last ones to finish developing, and that's just before they erupt (late teens to early 20's, provided they have enough room in the mouth to erupt). As a rule of thumb, teeth are fully formed shortly after they erupt into the mouth (the apex of the tooth closes shortly thereafter), so since the 2nd molars (12-year molars) typically erupt ~12yo, the apices close around 13.