The declaration essentially applies only to the Pacific map, so
- the declaration itself has no Mongolian implications, it just permits Russia to enter China
- they still can’t invade NWP or leave Russia on that map, until Germany declares or Japan attacks US
3) The NO I think is for war on the West map, so only during war with Germany v Russia
The declaration is gratuitous–make it every game. Russia v. Japan. no movement of pieces is required and no NO is directly affected by this, it simply allows you in to China. It would of course also be required to attack Japanese territory, if you dare do so R1-R4. I don’t think you can enter UK PAC either, until Russia is at war with both Germany and Japan.
It is the attack on Korea, Manchuria, or a Japan controlled territory next to Mongolia that implicates those rules, not the declaration of war.