yes beacose it adds weight to the plain
Yes, weight may affect a paper airplane by increasing its mass. This may alter its glide ratio and change its wing loading.
The wind can push the airplane in all driecrions which causes the airplane to go crazy.
yes. if you put it on one of the wings and try to fly it, it may tilt a little bit. it will affect the course you want it to take.
Yes, the design of a paper airplane can effect its performance.
if you place a paper clip on your paper airplane, you may find it improves performance by equalizing the load (weight) and lift (what the wings generate)
The heavier weight of a thicker paper will affect the range of the flight, and different folding characteristics and stiffness will affect the aerodynamics.
Yogurt
god
The effect of a hole on a paper airplane would depend on the type of paper airplane the hole is on, and where it is on the aircraft.
The weight of the paper. If you accumulate a lot of paper at one place (depending on the design) it could bring the airplane down faster than if you didn't accumulate so much paper in one place.
Not so much the shape of the nose that affects the flight of a paper plane, but the weight. If the weight of the plane isn't distributed properly the angle of attack is too small or to large making the plane nose dive or stall. Make sure there is weight in the center of gravity of your model.