Why Tower climbing is one of the most dangerous parts of the hobby, and safe practice requires all three elements together. Training teaches you how to inspect the structure, move safely, and recognize hazards before you leave the ground. An approved climbing harness (full-body fall arrest harness) is what actually holds you, and it only protects you if you stay tied off to the tower at every moment, including while moving from one position to another.
Watch out Each individual choice is a genuine requirement, so picking just one leaves out the others. A harness with no lanyard attached, for example, stops nothing during a fall.
Tower safety questions: if the choices are all sensible precautions, the answer is all of them.