What if they had kissed by the lake - would it have broken the curse?
Maybe not? Rupert is still hiding his identity at that point and that was really the number one barrier between them. Amir has no idea that he's actually kissing the Prince of the West. Also, the prophecy was very explicit about the curse being broken in the Hollow in their 18th year. Had they kissed, I imagine events would have played out basically the same except both of them would've been even more heartbroken.
Although… Imagine an AU where time/location isn't as specific and them kissing by the lake DOES break the curse!
*They kiss at the lake*
Amir: Whuh? What's going on
Bastard Kings in the distance: WHAT?? WHAT IS EVEN HAPPENING?!
Rupert: Oh yah, by the way… I'm Prince Rupert. Soooo… guess that prophecy wasn't about murder?
Amir: I am both upset and incredibly relieved.
The Queens: Welp, one of our boys is dead. Guess we go find out which one.
Atossa: You're both alive!
Lavinia: My son is gay?
Chamberlain: Called it.
Okay, but like, didn't Rupert have no idea what the prophecy was until after he revealed his identity? So it would be more like:
Cue confused screaming from both princes as they try to figure out what the heck just happened.
Or! They kiss in Episode 6: The "we shouldn't be hugging" scene. GASP that scene happens after midnight, therefore fulfilling the "eighteenth year" part of the prophecy! And weren't they basically already in the Hollow at that point?
Maze of thorns technically…
Amir: We shouldn't be kissing
Rupert: Well, I can't kiss you lat -- wait what's going on with the forest?
@cloudcover23 @oftheflamingheart @fluctuating-fangirl