
Yes, the ML is the Crown Prince. Their current-time relationship halfway resembles The Villainess Reverses the Hourglass (ie, he treats our lady with respect).
As for spoilers (about their relationship in the previous timeline)
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He loved her even in the previous timeline, but had to pretend he didn't to protect himself from his enemies (such as the Duke/fake dad). He knew from before they got married that she wasn't really the Duke's daughter (whom he hated), but he wasn't able to ask her who she really was, and she wasn't aware that he figured it out. So the love of his life died without his ever learning her name...
In the novel, he does manage to get his son back from the Duke and the real Veronica, and tell him all about who his real mother was as a person. No idea if he was able to raise his son to adulthood, though, with the Duke being...well, the Duke.

No, they're currently only feels like a close friend and then married for the best of their country (to weaken the duke's influence). In this timeline, she continuously rejects his proposal to be his empress but maybe in the past timeline she later agreed out of conscience. The crown prince's true love is Elena only both in this timeline and the previous ones
So is the ml the crown prince? Did he love our FL?