I agree with A, B, C1, C2, C3 1,2, but I have some doubts about answer 3, i.e. that with the ride-by-attack I have to pass on the "SQUARE" next the target. And this is precisely the reason for my post. If this were the case, i.e. I have to pass to the side, the rider would be too advantaged, because instead of a single trajectory for the charge (straight line), he would have 5: 10 feet to the left of the target with reach weapon, 5 feet to the left of the target, straight on target, 5 feet right of target, 10 feet right of target with weapon reach.
In my opinion the ride-by-attack feat doesn't have to overturn the restrictive rules of charging, it simply allows you to overtake your opponent like in the joust. As you said, in the joust you pass next to your opponent, but always in the SAME SQUARE, not in the adjacent square. SPACE (which is the space managed by the target) must not be confused with the space actually occupied by the target within the SPACE. I made a couple of drawings that show the concept of the difference between SPACE (token) and the space physically occupied by the creature. The pictures show in my opinion how ride-by-attack should be interpreted:
In this way both the charge rule and the ride-by-attack feat are respected, and the rider would be forced to follow only one single trajectory. Overrun is not mentioned in the ride-by-attack feat simply because the charge is already a full-action and would not allow you to use another standard action (overrun) unless using specific feats (for example "charge through"). In charge through, in fact, the overrun occurs in the movement (obstacle along the trajectory) and not in the target that is charged. What do you think about this?