Ti02

In the novel, Hanmei was 5 years younger to the Princess.

The Princess's husband was not a ruler, he was a general. They also had a daughter, who was engaged to the current crown prince. But in the drama, there is no mention of a daughter, in her place there is Song Tuan girl who is engaged, but she falls for FL's brother. In the novel, there was no such thing, FL found out that the current crown prince had affairs, and told it to the Princess, who then dissolved her daughter's engagement with crown prince, leading to their friendship.
The current king is Princess's brother. In the novel Hanmei would kill him, and become the ruler, and he was a really bad ruler, kind of a traitor. Even that general husband of Princess was killed by Hanmei earlier, but she didn't know that.

The novel was excellent. If you have time, you can give it a read. I don't know how much of it would be followed though.

Yes he is. His other identity was Zhao Yue. In the novel, he only loved the Princess.

Bad guy.

There is a lot off about him. You would see that in upcoming episodes.

Yes you are correct. When she asked for his help they weren't together. The guy left her when he went to exile, despite the fact she followed him. He in later episodes, says he wanted to give official exam again in order to give justice to his family.

Also, Hanmei supposedly is royal blood, like the true royal blood, he was at sometime Crown Prince too. If I am not wrong his family and the Princess family were relatives kind of, and they had trouble, inner fights, which lead to some killings. Hanmei survived, took another identity and became Princess's male consort after killing her husband. But he was a really bad ruler when he became one. Also FL's ex's family actually had the responsibility of saving Hanmei, because he was true blood, and hence his entire family was executed by Princess's brother (current king). So ex originally supports Hanmei, but he changes himself later because he realizes that Hanmei was ruining the country.
But it was implied that both Princess and Hanmei truly loved each other, so their ending was kind of tragic, but I couldn't say that he didn't deserve it.
But again I have no idea how much of this can be actually shown. There are other leads, there are military problems, there is a complicated love affair. The novel was around of 200 chapters. I told all this for context. But the makers can change the character in order to fit in 40 episodes.

Yes he is kind of a male consort. If they follow the novel no, the Princess stays as a positive character helping and supporting FL and ML.

If I have to tell you everything, its going to be a book. But you can watch for the couple, they are going to be together till the last, if they follow the novel. But Hanmei has another identity, he is pretty much the main villain. In the novel, Hanmei killed the Princess's husband, and would kill her brother (yes the king), he is a bad ruler, shakes hands with traitors of the nation, basically does everything bad. So the lead couple, FL's ex all come together to bring him down. The Princess, supports them after knowing the truth, and she tells him she is pregnant(when she is not), eats a kind of a medicine which poisons a person who would be intimate with her, basically poisons Hanmei over time. The main agenda was that he would slowly die, and they would bring someone's child (presumably FL and ML's child) and declare that he is the royal blood. So at the end, he knows he has no child, and he dies.
But honestly, I don't think so much can be shown in a drama, because other than this, there are a lot of subplots as well. The novel did not focus on society's problem with their forbidden affair, it was just by ML's mother, for a few chapters. Here ML's mom is dead. But according to the trailer, they fight for their love. Like the main focus is their love. So because already the drama has made so many changes, I don't think the end for Hanmei would be same as well, but yes he is the villain. So my suggestion is to watch the drama to understand how they would deal with it.

If they follow the novel, Xue Hanmei, is a very big part, has a very important role, also they are a couple. But I am not sure if you really want to know everything about Hanmei, because that's pretty much the main turning point/plot twist.

Also there was something like his entire family was executed, he was about to also, but FL's father saved him. He was sent to exile, where FL followed him, but he refused to be with her. According to him, he wanted to take the official examination again and become powerful to give justice to his family. When FL's father faced injustice, she asked for help, but he didn't (but I don't understand the injustice, because I thought her father died in a battle) Then he went on to marry Duke's daughter.

I loved it a lot. Maybe if you have time, you can complete. Ep 5 is pretty early, it gets so much better with each passing episode. For me, it met everything I liked, there's was a revenge saga, really cool ML FL, really pretty chemistry despite an age gap, pretty aesthetics, excellent villains, no major angst, and a happy ending. It was very satisfying as well, everyone got what they deserved. But then as I said, it was my first Chinese costume drama, I can be a little biased, but at that time it was really popular, and my friend recommended, and I was not even into Chinese dramas at that time, and now I love the costume dramas so much.

Its 12 and 13.

Its adapted from a novel where the rebirth was the first plot. Secondly what you see here in the synopsis, was edited later after the release of the drama. It clearly stated rebirth, so most of the people who were anticipating its release, had the rebirth conception in mind. But after the drama released, people understood, that the synopsis was just copy pasted from the novel's synopsis.

You're welcome :)

I understand. Thank you!

Not to break your heart or something, I read the novel, and even if they followed it, the result would be same. She goes back in the past, doesn't marry her boyfriend, instead marries Wei Jun in a social ceremony, but isn't able to save him, his brothers and father. Its all about how she guides the youngest brother in becoming a general, and giving Wei Family its previous glory, and then falling in love.

Yeah then I have to spoil it for you. So this drama is adapted from a novel. Before the release of the drama, the novel's synopsis had been copy pasted in MDL. You can check the current MDL synopsis, WeTv synopsis for a better understanding, but I will mention it as well.
The makers did some changes in the drama, due to the fact that rebirth is censored in China, so they had to make it a kind of dream sequence, so they completely omitted it.
Here, Chu Yu had an ex boyfriend Gu Chu Sheng, who did not support her and got married to a Duke's daughter. Chu Yu's father died in a battle and her brother was heavily injured, all because of a traitor who leaked their information and a kind of weapon to their enemies. So she wants to find out the traitor. She proposes marriage to Wei Jun, the eldest Wei brother, because Wei family was the incharge of the armory where the traitor is. Wei Jun promises to find out the traitor, but they are just friends. In a battle, the entire Wei Family dies, leaving only the youngest/7th brother Wei Yun. Wei Family's reputation is tarnished, and they are blamed for killing 70k soldiers, and taking up offensive approach rather than defensive against the enemies. Wei Yun is also arrested. Chu Yu declares/lies that Wei Jun promised her marriage, and does a self declaration to be wife of Wei Jun, thus kind of marrying his corpse. She bails out Wei Yun, and though they have initial suspicions over each other, they soon join hands to find out the traitor who destroyed both their families, thus falling in love, and having a forbidden love affair as well. Mixed with elite military, noble families, palace politics, its like 2 people together to protect themselves and their nation.
This is the drama all about.

Honestly that was my first chinese costume drama. So I might be a little biased too. But I never liked something more than that.