Chokdee,
Your questions suggest that you are preparing for the JAR ATPL exams. The answers below are based on the "conventional wisdom" required for those exams.
INCREASED CLEARWAY
The effect of an increased clearway depends on what exactly is limiting your mtow. If it is the ASDA or TORA, then the extra clearway might have little or no effect. Remember you have to get from V1 to VR and VLOf within a specified fraction of the TORA, as well as reaching at least V2 by the end of the TODA. You really nead to look carefuly at the question to see what kind of situation the examiners have in mind. The clues are often in the options, rather than the question itself.
C OF G POSITION
The entire allowable C of G range is in front of the neutral point. The futher forwad we move the C of G the greater will be the tail down force required to keep the nose up. This increases the stalling speed and trim drag. So range goes down, as C oF G moves forward. It does however make the aircraft more stable.
Moving the C of G aft within the allowable range reduces the need for tailplane down force, so the trim darg and stalling speed reduce and range increases. But stability decreases.
STATORS
In an axial flow compressor both the stators and rotors form divergent ducts. The rotation of the rotors accelerates the air, while the divergent ducts between the rotor blades decelerates and compresses it. The overall efect is that airflow velocity goes up in the rotors and down again in the stators. The pressure and temperature go up both in the rotors and in the stators.
TURBINES
The shape of the ducts between the stator blades depends on the type of turbine.
In a pure inpulse turbine the ducts between the blades are convergent in the stators and parallel in the rotors. This is because impulse turbine rotors extract energy by changing the direction of the airflow.
In a pure reaction type turbine the opposite is true. The ducts in the stators are parallel and those in the rotors are convergent. This is because the rotors in reaction turbines extract energy by accelerating the gas. It most not go supersonic, so we really don't want it to be going too fast when it enters the rotors.
In a real gas turbine engine the turbines are a combination of impulse and reaction. They tend to be mainly impulse at the blade roots and mainly reaction at the tips. So the ducts between the stator blades are convergent at the roots and parallel(ish) at the tips. This is the type of turbine the examiners mean when they ask about an "impulse root turbine".