If the USSR is not at war in the pacific then no, the rest of the allies cannot land planes on USSR territory in the pacific half of the map.
Of course, the USSR can declare war on Japan from turn one with no consequences, so there’s really no reason not to be at war since all not being at war does is limit your options.
It’s non-combat, and must be a land unit (AAA don’t count). They can land planes there, but to claim the territory as their own, they must land an Infantry, Artillery, Mech, or Tank unit.
The AAA unit doesn’t fire during bombing raids. Facilities are assumed to have built in AAA which fires once during a bombing raid. AAA units get one shot at the beginning of a defensive battle involving attacking planes, and after that they can be taken as casualties as normal. If you attack an AAA unit on its own using aircraft, the AAA gets 1 roll to try and kill the plane(s). If it misses, then the AAA is dead.
1. If the transports are on their on, then they are sunk by the fighter, yes.
2. When the defending fleet is defeated, the transports die with it. However, if you are attacking with subs and the defender has lost all of his warships, but still has planes left, then the transports can be taken as casualties for the sub hits while the rest of the forces fight it out.
You can retreat as long as the sub didn’t start in that sea zone that turn. If the sub came from another sea zone, then it can retreat from whence it came.
The problem with this strategy is that it’s hard to win the game this way. There’s three victory cities you need on the mainland, and if China controls all of it for a few rounds then it will later be very difficult for Japan to get back onto the mainland, as China will have a lot of troops with nothing better to do than guard those victory cities.
There is also a surprising amount of money to be lost this way. All those little territories add up. There is also no real reason to abandon China since it’s entirely possible to grab all the money islands while at the same time killing China.
In some circumstances it can be worth it as the UK to declare war on Japan first in order to get the bonus money for UK Pacific and Anzac.
It depends on the enemy. If you’re fighting against Russia, then bombing raids are better. If you’re fighting against Japan, then Convoy disruption works better.
The French fighter that starts on the UK is also a great way to remove those blockers and give Germany a nice surprise.