Some corrections and further explanations (no time limit):
1. A mirror flips the direction perpendicular to the mirror. Left is still left and right is still right, e. g., your left hand will still be on your left side in the mirror. But, your mirror image will be looking in the opposite direction compared to you.
7. The pigeons are flying around inside the truck. Doing this they exert a force on the air around them which in turn will exert a force on the truck containing the air. On average this force will balance the weight of the pigeons. Also, 200 pigeons at maybe a 200 grams each is just 40 kg to be compared to the weight of a truck of several tonnes.
9. Using spherical symmetry and the divergence theorem we can conclude that the gravitational field inside a spherical shell is zero.