Responses

They are still but honestly what you’re saying isn’t that unusual in this setting
They are in a political marriage that probably needs the kings approval to annul.
Since it’s political, it’s not unusual for them to have actual partners even while being engaged. It’s not a great look per se but because they are both doing it people probably don’t think much about it.
Though it looks like now the plot is moving forward and the engagement is meant to be annulled.
Anyway, it’s not like they’re going to get married. That’s when it would be absurd
Are FL and the prince still engaged I don't think I remember them breaking it off. It'd definitely be the height of stupidity if they still were. Since they're both publicly with different people and the FL isn't even in a position where she can be crown princess because she's supposed to be succeeding the duke.