9, 29, and 30 for the headcanon ask. Rogue/Gambit.
9. What’s the most embarrassing thing they’ve done in front of each other?
There’s probably a canon answer to this, but it IS a headcanon game, so...headcanon it is. These are purely my own ideas; none of this has occurred.
For Gambit: I feel like he’d be the type with an irrational fear of bees. No deathly allergy, no real reason to hate bees - he just really does not care for them. Hence, his most embarrassing moment in front of Rogue involved being so flustered by the sight of one (1) bee by a pool that he fell backwards, crashing into a flimsy pool chair by the edge of the pool, which ended as one might expect. After realizing why he’d fallen in a pool, Rogue refused to let him live it down. She still sometimes texts him pictures of bees to remind him of it when he’s annoying her.
For Rogue: pre-relationship. Hers is definitely inadvertently spilling the minutiae of her attraction to Gambit (which she hadn’t yet admitted) to a random person in a bar while drunk, not realizing in her inebriated state that Gambit was sitting a table over and heard everything. The ensuing conversation was...awkward, to say the least: he’d known how she felt and she knew it, but the fact that she’d admitted it so bluntly was rather humiliating.
(Can Rogue get drunk? I feel like there’s probably a canonical answer to this, but I’m going to say she can.)
29. Why do they fall a little bit more in love?
For Gambit: Rogue keeps him on his toes. Most of the women he’s had relationships with took zero effort to win over, but Rogue is nothing like them. He has to go to great lengths to win her heart; Rogue wants something real and lasting that his past lovers largely haven’t, so she doesn’t make it easy for him. And she’s not starry-eyed over him, either - she knows he’s met his match in her and doesn’t intend to let him forget it. It would be easy to call it the thrill of the chase, but it isn’t quite that. She makes it difficult for him because she wants to see him be a better man than he has been, and she stays with him because she knows he can be. He hasn’t had many people see him as a good man, or someone who could be one; Rogue does. He loves that she sees him that way, but more than that, he loves that she gave him a reason to live up to his potential.
For Rogue: this is tied to Gambit’s reason and isn’t technically ever said in canon but I feel like it could reasonably be extrapolated from it.
Gambit obviously has a long and storied romantic history, most of which isn’t her favorite, but the fact that he was willing to turn his back on his former life when she showed him that that’s what it would take to earn her love is a huge part of what made (and still makes) her fall for him. He’s still extremely difficult to be in a relationship with sometimes, because you can’t undo years of bad habits overnight, but he’s trying. He’s tenacious in trying to prove to her that he can be the man she deserves and the fact that he loves her - of all the women he’s been with - enough to essentially throw away his past self is what lets her know that she wasn’t wrong to fall for him. (Oh, and his cooking doesn’t hurt. Nor does the French, or his sense of adventure, or the fact that he has a surprisingly nice singing voice and he’s the most adorably smitten cat dad in the universe...)
30. Why does it work (or not work) between them?
Well, everything I listed above, plus intense attraction, similar personal histories (helps give them common ground), and the fact that both of them are way too stubborn not to let it work out.