for the flags, you have to go in each ship's folder and find the .visual file that contains the name and position of the flag, and change the name. you can open these files in any text editor, and the flag info should be in 2 different files and you have to edit both. from a quick look, the soviet flag is RM001 and the tsarist flag is RM057.
the eagle and the red star aren't separate objects, they're painted on the texture of the ships, so you would have to edit these
if you want an easier way to replace the flag, you can just replace the soviet flag texture with a copy of the tsarist one. they're in res/content/gameplay/russia/misc/textures
