Manual?

2. The refreshes regenerate as you play the game. The more enemies you kill, the faster they regenerate.

3. You don't get any emblems from Conquest. You get 5 emblems from campaigns. So when you beat the game, you can finally buy a tier 3 general. Although you won't need him since you have to beat the game to get him. You can use real money to buy emblems though.

4. Years ruled is calculated by finishing a conquest. It's factors are: Total resources (food, industry, and gold), how many turns it took, and possibly campaign stars. That hasn't been completely confirmed though.

5. The upgrades increase the stats a tiny bit. If you buy the tier 1 upgrade for a unit, it will become unlocked for use in THAT CAMPAIGN ONLY. So don't invest everything into 1 campaign because it doesn't carry over into other campaigns.

6. The two pictures are Rank and Nobility. The rank effects bonus hp and Nobility effects HP regen per round.

9. You get medals from beating campaign missions. You can get 50 from each mission if you get 5 stars. Medals are occassionally awarded when you kill units. Not all of the time though. Beating conquests can give you anywhere from 60 to 100 medals.

Sorry I can't answer them all.

I'm not sure if my answers are right, but I will just try to answer the questions that weren't answered.

1) If I'm not wrong, you are supposed to press the tick at the bottom left of the options screen. You may have just pressed the "X" to save the options, but it will not save the options this way.

8) I don't think there's an estimate of the damage each unit can deal, but when creating troops or checking each troop's information, there is some information on the damage of the troop. For example, it is stated that Light Infantry damage is "3-6" or Grenadier is "2-7". I think this just lets you compare the strength of different units. (Correct me if I'm wrong)

I will answer these questions based on my understanding. Anyway I just changed the font to this color because the old color is difficult to read. 

1) Main menu > Options
- The HD Mode and Grid are always not selected even after selecting it. Why?
I don't have this problem so I do not know. 

2) Main menu > Headquarters
- I am presuming the button below the generals is a refresh button that gives you a different pool. Do these refresh buttons "regenerate"? - i.e. after you use the two refreshes, then what?
You will earn one "refresh" from every a 100 kills (i think)
- I think I read in the forum that you can only get 4 emblems from the Conquest mode. Does that mean the 3-star generals can only be purchased with real cash?
You can get 5 emblems from campaigns and one more at the start. That makes it 6 emblems so, assuming you get all of that, you can buy a tier 3 general who costs 6 emblems. 

3) Main menu > Achievement
- How is the years of rule calculated?
I do not know how exactly. But we do know that it is mainly based on how fast you complete the conquest and how much resources you have at the end. Other factors such as player's rank/nobility and campaign progress can affect the year rule too.

4) Campaign > Upgrade
- What benefits does an upgrade provide? Does the unit stats increase? Does the unit get cheaper?
The first level upgrade allows you to build that type of unit. The following level makes that type of unit starts with higher level (chevron).

5) General
- What do the two icons below the general picture mean? Does the number below the heart means additional bonus to the unit health?
Heart means bonus health a unit will get (on top of its original health) if it is commanded by the general. Another one is health regeneration per turn.
- Does the general experience carry over from a mission in a campaign to the next? Or does it only apply in the Conquest mode?
Yes, general experience (rank and nobility) is independent to campaign or conquest. It will be carried over.
- What about the archery icon in the bottom right?
And option to increase level (chevron) of the unit that the general is commanding. Max level that can be achieved from this option is equal to the number of training stars the general has.
- What does each star mean? +1 to attack?
To put it simple, 1 star equals to additional 5 damage. For further information please read european-war-4.boards.net/post/14095
Thanks to wangchengxy for the information.
- Can you detach a general from the unit that he is originally allocated to and assign to another?
Unfortunately, no.
- In the Campaign mode, the item that a general possesses cannot be selected to see what bonus it provides. Any way of doing it?
You cannot do that on generals that are not yours. If you want to know what bonus you'd get from items, please check european-war-4.boards.net/thread/587/item-stats-locations
- Do you need to level up trainer generals for them to be more effective in regrouping? Do generals only get more stars by regrouping?
You general only get more star from regrouping. An portion of experience (rank and nobility) from trainer general will be transferred to the target general.

6) Unit
- What do the coin and wrench figures below the soldier picture mean? Maintenance cost?
They are cost to produce that unit.
- What does the "soldier group" icon (the top icon on the second column, above the meat icon) mean?
That's formation. You can think of as when you go to a burger shop where you are offered a S/M/L size of burger for different prices. A formation of 3 infantries (like an L size burger) has more health, a bit more damage, and costs more resources. 
- When you select a unit, what do the archery and the "arrow pointing downwards to something" button (when you click it, it says it costs 40 coins) do?
I guess that your "something" is a ship. A land unit has and option to be equipped with carrier which allows it to move into the sea. 
- After few combats, a unit can earn a stripe. What benefit does it bring? There doesn't seem to be any stats increase. How do you know how close a unit is to get a stripe?
I am not so sure about this. But one thing for certain is that the unit recover some health after get promoted (get more stripe (chevron)). 
- If the unit does not have a general, will it never recover health unless stationed in a city?
The unit can also get healed at stable, factory, and port. european-war-4.boards.net/thread/462/regeneration-rates
- Contrary to what it claims, the siege artillery does not seem to do much damage to fortresses or cities. What am I missing here?
It indeed deals extra damage to fortresses. For bonus damage against each unit type, check here. european-war-4.boards.net/thread/459/unit-bonus-penalty

7) City
- Does the city level impact healing rate? Do units stationing at cities that produces the same type get additional healing bonus (i.e. an infantry unit stationing at infantry-producing towns)?
Higher level city heals more health. Again, you can check it here european-war-4.boards.net/thread/462/regeneration-rates
- Can you change the type of unit a city produces?
No. City produces infantry, stable trains cavalry, and factory builds artillery.
- Does a city provide defensive bonus against attacks?
Yes. You can check the reduction rate at the shield symbol on the top left corner under your currently resources.
- What does the "shield with the all" icon at the top left mean when you select a city?
Damage reduction bonus from the city.
- Some units have a different stats next to the soldier group icon. For example, Light Artillery has a solid soldier and a grey soldier next to the icon while the heavy artillery only has one solid soldier against it. What does this mean?
I am not sure about what you mean. Maybe you need to give more example or picture.
- Why are some of the units (the most advanced ones such as machine gun) cannot be produced even when you have sufficient coins and wrenches?
Normally, you can produce them in conquest. But in campaign, the available unit types are limited by your tech-tree. If you want to use a machine gun and it is not available for your nation, you need to spend stars (you received from campaign missions) to upgrade your tech-tree.

8) Combat
- Is there any estimate that shows what is the likely damage that a unit will do and get in a combat? It just seems so random
You can check it from european-war-4.boards.net/thread/925/respond-chinese-players?page=3

9) Medal
- How do you earn medals? Do you get one for every unit kill? Every city captured? I played the first few campaign missions, but can't seem to understand the logic behind it
You can earn medals as rewards from completing each campaign mission. Sometimes, you also get medals when your troop make an attack.

Wow. Thanks so much for the answers. I have added pictures to help clarify my questions.

Screenshot 1: I believe kanue is saying this is formation and simply implies more number of soldiers to the unit. Not sure if more bodies always means more expensive as the heavy artillery has only one formation (compared to the light artillery which has 1 1/2 as shown in the image), but costs more



Screenshot 2: Again, based on what kanue said, those buttons are upgrade unit and equip unit with a transport ship?



Screenshot 3: How do you know Napoleon in this example is close to (or far away from) advancing to the next rank/nobility? Napoleon has three stars against the archery (training?) icon. Does this mean his troop can have up to three stripes?



Screenshot 4 & 5: These two images show same line infantry units, one without any stripe (top) and the other with one stripe (bottom). I don't notice any improvement in stats...






P.S. I actually thought the damage reduction bonus was a penalty (e.g. thought a -20% cavalry was a 20% penalty to defense) and was trying to move units to hexes with lower figures!

Screenshot#1
You'll be able to have double formation for the stronger units after upgrading the buildings (factory in Your example).
For the infantry units You can have triple formation in towns.

Screenshot#2
Yes and yes.

Screenshot#3
As Mountbatten explained the bar will be filling up for the generals that You have in Your HQ.
The stars in training ability show how fast the unit with the particular general assigned will be receiving the training(upgrade) icon during the mission/conquest. Some skills (like War Expert, War master) can also influence that.