1. You either declare war or are at war by someone declaring on you(i.e. already at war). Convoy raiding only occurs if at war. Regardless of if you had a chance to fight yet. (Meaning they declare war or actually attack your units, and during their collect income phase your subs destroy IPCs. Even if you have not had a turn yet.)
2. If the fighter lives, it won’t have any movement and the carrier will be required to move there for it to land. If the carrier does not move in (unable to) then the fighter crashes, hopefully you can assign a hit to destroy the fighter if you do not want to move it there. During retreats, land and sea units move to a friendly/non-hostile territory they came from. Air units have always remained and landing normally during non combat. Therefor, I believe the plane would crash during non combat as it has no additional movement and there is no landing space if the carrier is not there to “catch” it. The only example of planes receiving 1 extra movement are defending planes who have their carrier destroyed, they have 1 movement space to land or crash.
3. Yes the Chinese territories shaded orange on the board (i.e. Japan’s starting territory color) are “originally” controlled by Japan. (Manchuria, Jehol, Shantung, Kiangsu, Kiangsi, and Kwangsi) the other eligible territories are (Siam, Korea, Japan, Okinawa, Formosa, Hainan, Iwo Jima, Marianas, Marshall Islands, and Paulau). Remember the allies can control it first, you get the once per game income when an Anzac unit lands either during combat or non combat.
This is not official, but it is the way we play it in my group. Krieghund is the user name of the guy that writes the axis rules. His replies are axis “gospel”.
Edit: Krieghund answered while I was typing this up….bad timing on my part.