Copy-paste from the in game rules manual
Poland (Grand Duchy of Warsaw)
Any Major Power may create Poland.
Poland Components
Russian, Austrian, and Prussian provinces marked on the map with a “(P)” are the available Polish components.
The following is required in order to create Poland: Masovia (Capital) and any ONE of the following: Danzig, East Galicia, Lithuania, Podolia, Polesia, Posen, Volhynia, West Prussia, West Galicia, and White Russia.
NOTE: To create Poland, click on Masovia and then click the “Create Kingdom” button. The program will add all the available components owned by the Major Power at the time of creation
Ø Once created, Poland is a normal minor Free State of whatever size that has been determined and the combined money and manpower values of its component provinces are doubled in value (as in any minor Free State and used for the usual purposes).
Ø The Polish minor Free State may only be conquered by the unbesieged occupation of Warsaw for a month (Polish provinces may not be individually conquered), after which the provinces that were part of the Polish Free State are considered unceded provinces, if controlled by their home nation Major Power, or ceded provinces, if controlled by another Major Power.
Ø The conquering Major Power may, if desired, again declare Poland a minor Free State during any later Economic Phase.
Ø If Poland is ceded, either voluntarily, or as a peace condition, it must be ceded as a unit. The controlling player may not separate individual Polish provinces for individual ceding or other purposes. When ceded, the component provinces become ceded and/or unceded provinces, depending on the controlling Major Power.
Ø Poland is worth “+1” political point to create or to conquer (capture Warsaw). The loss of a controlled Poland costs “-1” political point, whether to conquest or by ceding to an ally.
So when Prussia created Poland it gave it Masovia, plus all the other Polish provinces Prussia controlled. (Posen, West Prussia, Danzig). Poland was never listed in the provinces to annex listbox in the surrender conditions, but the individual provinces were. So I ticked the boxes for the three provinces I wanted, and choose Posen, East Prussia and Masovia. I ended up getting all 3 plus Danzig and West Prussia. At that time I went and read the rules regarding Poland and decided that everything worked as written (although perhaps in a slightly clunky way, since Poland was never mentioned in the surrender terms). When I grabbed Posen, the game gave me all 4 Polish provinces. Hence Masovia was not eligible.
Regarding still being at war with Poland, in the France-13 save you have.

- Screenshot 2024-07-15 201140a.png (113.61 KiB) Viewed 456 times
A bit of a minor issue, but most of the time Prussia probably should not create Poland before about 1812/1813, as under these rules (which seem different to my memory of the rules when we played face to face), it just loses too much of it's home nation manpower, and it is too easy for someone else to take Poland even a conditional surrender. After 1812/1813, it is less of an issue, as there will probably only be one more war with France (or whoever is winning), so It might as well pump out Polish troops. (If Prussia get to Dominant Power Status, then it maybe it can defend Poland well enough to be worthwhile creating, but it probably still doesn't want to lose all that manpower).
Regarding Finland, I understand you are no longer at war with Sweden but Finland has been conquered in other games before Sweden is conquered. AI Russia should have moved to conquer Finland, so I'll look at this again.
Finland being conquered before Sweden is fine, but if Russia conquers Finland without having a corps in Sweden, the Russo-Swedish war will lapse. Not an issue in this game, because Russia was at war with the major power controlling Sweden, but something the Russian AI should avoid in the more general case, hence there is a reason the Russian AI might be programmed to not advance to Abo before Russia gets troops in Sweden.
Quotes from the in game rules.
6.15 Lapse of War with Minor Countries
If a Major Power has no corps within a minor country they have declared war on, then that Major Power is considered to be no longer at war with the minor country and must be at war with the Major Power controlling it before he can attack it again. (EXCEPTION: The program will not recognize a lapse of war if the minor country has forces inside of the enemy Major Power’s territory.) Any garrisons, Cossacks or Freikorps are repatriated. For multi-district minor countries, this applies if a secondary district has been conquered and there are no invading Major Power corps within the rest of that minor country.
10.7 Conquest of Minor Countries
Conquests of minor countries are checked for after all Major Power sequences are completed. Control flags are changed to show the conquest of minor countries and their change of control. The control flags are changed only if the capital of the minor country was occupied during the previous month and the conqueror has maintained uninterrupted and unbesieged occupation for the entire current month. A newly conquered minor country is always marked with a conquered control flag.
NOTE: The lapse of war check (6.15) occurs during the Diplomacy Phase. The conquest check occurs at the end of the Land Phase. Therefore, conquest requires having a corps remain within the minor country to prevent lapse of war plus one full month's occupation of the capital. This means from your own Land Phase in which you first occupy the capital through the end of your next Land Phase. If the minor capital garrison is eliminated during another player's Land Phase (e.g., the garrison fails to forage), that does not count for your conquest purposes.
I actually think that note is slightly misleading. You need a corps in the minor during the Diplomacy phase to prevent lapse of war with a minor, but provided you controlled the capital at that time, you are free to move the corps out and just leave a garrison to conquer the minor at the end of the land phase. (Assuming no other forces actually intervene).
France can actually use this and its ability to move last then first, to spread out, siege a lot of enemy controlled minors, then move first to concentrate and make enemy major powers either send out unsupported corps, or lose minors.
And lastly, Gibraltar. As a minor nation, I think you may need a corps present for a turn to convert control? I tried advancing your game to move a corps into Gibraltar and also landed all of your amphibious units into Wales, but Great Britain surrendered before I could see what happened with Gibraltar.
Gibraltar did become French controlled about the time Britain surrendered. (I can't remember whether it was at the end of a land phase, or whether Britain went unstable. I do remember it took longer than I had expected, but I didn't notice when Britain failed it's forage roll, and hence maybe didn't start tracking the change of control from the correct time). The bug report was more to point out that the British navy was still able to use the port, even though I controlled the port guns.
I have a save from around the time of the Cossack issue, but unfortunately I can't get it to reproduce. (It wasn't a major issue, more an annoyance). If it happens again I'll get you a save.
Thanks for you work on this.