Our ML's real name is Zhang San in the real world, and he got transmigrated into Xiaohou Dan's body since middle school. The actor who plays ML as a child was also used to play the current crown prince.  I guess it's convenient and since they're father and son, it makes sense they look like each other (so they can use the same actor to play different roles :D).  Dan and Zhang San are the same person, he was the one who planted those flowers. It was not the current crown prince, he is a different person entirely lol

I think they're different actresses, only the ml as a child and current crown prince is the same actor :D

One more question, do you know if Zhang San transmigrated as a kid or adult from the real world? If he transmigrated as an adult into a child's body, and I lived childhood twice. If, as a child, it feels a little off that he could know and act like a modern-day guy so well since he basically grew up in the palace. 

He was a child himself, transmigrated when he was in middle school. That's why it's so tragic, being in an hostile and dangerous environment, surrounded by enemies all his life. Meeting the FL many years later, when he basically had already lost hope :'( It fucked with his head, built up his tyrant persona having to be in survival mode all the time.

 KrayTran:

So when he told FL later on that he was an actor and not a CEO, that was another lie as well? 

Yes, he doesn't want her to know that he transmigrated much earlier than her.  The FL assumed he was a CEO and later actor, so he went along with it. Afraid of what her reaction will be, he thinks she will hate him lol Also because he has acted the part of the tyrant for years, he believes it too.

I think the confusion mainly comes from how the story reveals information little by little. Zhang San and Xiaohou Dan are the same person. We just see different parts of his life shown separately, so it feels like two different characters at first.

The casting choice also makes it more confusing. The same actor playing the child version of the ML and the current crown prince makes it seem like there is a deeper connection, even though there is not.

He transmigrated as a middle school student, so he basically grew up in that world. He did not live as a full adult twice. That explains why he acts the way he does and why he hides the truth later. Once you understand the timeline, everything becomes clearer.

In the end I see he returns to the real world as a fully grown adult with clothes... I guess that's never explained?