(2) Answer: No, because when point Q slides to point H, a triangle jumps, and because OH=4, QP (HP)=3, OP=2, QP? +OP？ =3? +2? = 13, what else? =4? = 16, what about QP? +OP？ ≠ oh Therefore, the inverse theorem of Pythagorean theorem is not valid, so PQ and ⊙O are not tangent.

(3) This question needs to draw auxiliary lines, and I don't know how to write the process here. Answer: 3 decimeters, 120.