A and C,
The asymmetric blade effect (p-factor) is noticed during take-off in a taildragger, but not in the way you imply.
P-factor is present
before the tail is lifted, and will cause a left-yawing tendency. Once the tail is lifted, the blades are symmetrical - as in a tricycle - and the p-factor disappears. The rudder required through take-off roll will be reducing throughout the roll due to increased rudder authority as speed builds - but there will be a marked reduction after raising the tail, due to the removal of p-factor.
Gyroscopic precession, which fujiflyer is talking about, also causes a yaw to the left. This is
only present
during the period when the tail is actually being raised - it is not present before the tail is raised (unlike p-factor), nor after it has been raised. This is dependant on the rotating mass, and I agree with you that fujiflyer may be confusing radial engines with rotary engines. Side note: from the pilots point of view, gyroscopic precession can be controlled by adjusting the rate at which the tail is raised. If the tail is raised quickly, it can be quite severe - a good reason to apply forward stick gradually.
This topic has now gone way off of Vfrpilotpb's original question about yaw due to power changes!
Both p-factor and gyroscopic precession are dependant power, but it's probably worth pointing out that, during the cruise, the primary (I'm tempted to say only, but I'd need to think about it a bit before committing to that) reason that yaw is encountered when changing power settings is neither p-factor nor gyroscopic precession - it's slipstream effect.
FFF
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