Stage 4 - Coup d'├ętat

Objective Changes & Effect
Defeat Cao Xun, Cao Xi, and He Yan before eliminating Cao Shuang. Unlocks Xiahou Bas Journey.

Simple objective, follow each mission and Cao Shuang should be the last one you need to kill.

Stage 4X - Xiahou Ba's Journey

Objective Changes & Effect
Defeat Jiang Wei quickly before he meets up with Xiahou Ba. Enables Xiahou Ba to appear in later battles.

Regardless if you're playing as Sima Zhao/Wang Yuanji or Guo Huai you should be able to reach Jiang Wei before Xiahou Ba can meet him.

Sima Zhao/Wang Yuanji
The quicker you defeat enemy officers the quicker Guo Huai can block off Xiahou Bas path making him take detours.

Guo Huai
Defeating enemy officers allows for you to approach two points on the field where you can make Xiahou Ba take a detour which will give more time as he will go the longer way around.

Stage 5 - East Gates Battle

Objective Changes & Effect
Escort all allies to safety. Unlocks Battle of New Hefei Castle.

A rather simple objective, in fact it is harder to get the event cutscene from this stage compared to the star.

Stage 5X - Battle of New Hefei Castle

Objective Changes & Effect
Defend all gates within the castle. Enables Zhuge Dan to appear in later battles.

Regardless who you pick this is a simple objective and the AI will carry their own weight as the morale gets to your side. Follow each mission though you can skip the one that would have you backtrack into the castle to get the weapons working.

Stage 6 - Mt. Tielong

Objective Changes & Effect
Prevent Guo Huai from sustaining injuries. Enables Guo Huai to appear in later battles.

This one can be a bit tricky to get, though try not to be too fast completing objectives as you may pass certain ambush officers. As the gates open defeat Jiang Shu to secure the main camp then make your way around the the East exit of the main camp, locate Li Jian and defeat him. When he is defeated he will steal some Wei uniforms as he retreats which he will use later. Xingcai will then deploy wood oxen which is a ploy for a fire attack, destroy the oxen and defeat Xingcai. Make your way through the South, but don't go all the way stop when you reach the cave like area as ambush units will spawn, defeat them then make your way to Guo Huai. Li Jian will have returned in Wei clothing defeat him before he tricks Guo Huai then meet up with Guo Huai.

Stage 7 - Guanqiu Jian & Wen Qin's Rebellion

Objective Changes & Effect
Defeat Wen Qin before Wen Yang. Effects Battle of Xuchang.

For this objective you will have to ignore Sima Shis order to pincer attack Wen Qin and Wen Yang after Wen Yang retreats from the Wei main camp. Take the Western mountain path into the main center area and defeat all officers that go for you after Sima Shi and Wen Yang have a conversation defeat his father first before you defeat him.

Stage 8 - Battle of Xuchang

Objective Changes & Effect
Complete all star objective of previous stages. Enables Wen Yang to appear unlocking the Hypothetical route.

Have all objectives complete when you reach this point in the story and talk to Wen Yang for the Hypothetical route.

Hypothetical Stage 9 - Capture of Chengdu

Objective Changes & Effect
Defeat all enemy officers before subduing Liu Shan. Unlock Defeat the Rebels.

Liu Shan has to be defeated last, this includes Guan Suo and Guan Yinpings arrival after you personally defeat Jiang Wei in the main castle.

Hypothetical Stage 9X - Defeat the Rebels

Objective Changes & Effect
Finish the battle. Enables Zhong Hui to appear in later battles.

Simple task as Zhong Hui will not appear until you defeat all other officers.