1. The blower turns stored energy into forward movement of air, for which there is an equal and opposite reaction, so the boat moves backwards. The air then hits the sail and pushes the boat forwards. There are very likely to be losses in this set of transactions so the net effect is probably a reduced backwards movement.
2. The plane absolutely takes off unless (a) you don't understand physics or (b) you choose to interpret the scenario in such a way that it immediately escalates to infinity and destroys the world.