Depends how early this is. Most of Micronesia is nominally Spanish, but it's prime expansion for Japan
As for Russia, that might be a way to unite Japan and China. Japan can grab Kamchatka and whatever bits of Karafuto/Chishima the Russians won't let them have.
Zero chance of that. Kamchatka (in Petropavlovsk) had the only good harbour in the entire Pacific seaboard before Vladivostok was acquired. I am assuming this is an actual POD in the early 1800s. if you give that up, you might as well give up the whole seaboard. Zero chance.
Also, in the 1800s, if things get really serious, Russia stops mucking around in Europe, cuts a deal with Napoleon/demands subsidies from Britain, brings a fraction of its Napoleonic army over, and stomps Japan's expeditionary attempts until it hurts. Getting to the Amur takes a long time but it's nothing like invading India in terms of "impossible".
Early 1800s Japan has a much bigger better chance of taking California. Or Hawaii. Or Micronesia. Provided the British are building and officer-ing their navy for them, which they would need anyway if they're taking Kamchatka.
For Korea, I expect the easiest route of expansion would be to the north, trying to take the Russian Far East (south of the Amur) and Sakhalin from the Russians? Like this.
Zero chance to the power of zero. That map requires defeating BOTH the Qing and Russia. Russia didn't even grab the Amur basin until 1855. So yes, it needs to defeat China, and then take Russia's only valuable harbour. And Korea, unlike Japan, isn't safe on its island. Russian or Qing troops can just, you know, do it overland. Any such war results with Korea, no matter how quickly industrializing post-1800, getting penned in and giving up concessions.
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