The OPERA experiment was designed to study nu mu -> nu tau oscillations in the appearance mode in the CERN to Gran Sasso Neutrino beam (CNGS). In this Letter, we report the final analysis of the full data sample collected between 2008 and 2012, corresponding to 17.97 x 10(19) protons on target. Selection criteria looser than in previous analyses have produced ten nu(tau) candidate events, thus reducing the statistical uncertainty in the measurement of the oscillation parameters and of nu(tau) properties. A multivariate approach for event identification has been applied to the candidate events and the discovery of nu(tau) appearance is confirmed with an improved significance level of 6.1 sigma. |Delta m(32)(2)| has been measured, in appearance mode, with an accuracy of 20%. The measurement of the nu(tau) charged-current cross section, for the first ti me with a negligible contamination from p(z), and the first direct evidence for the nu(tau) lepton number are also reported.