chewchew
You only need to do the pool scene with Desire once to unlock the possibility for the visit Desire at night scene. This assumes that you got her to the point where she invites you to come to her room at night so she can return the favor. If that is done, now you need to have seen all three lingerie. It seems like you have seen one. This could be the trouble.
Her choice of lingerie is random. If you visit her at night when her stats are high (she won't wear the sexy one unless her lust is high) and she doesn't wear the sexy lingerie, then hit <PgUp> to roll back until you get to where you were when you decided to visit Desire. Then change your location or open your phone. This will reset the randomizer. Then visit her again. If she's still not wearing the sexy one, reset until she is.
That said, there may be a secret criteria which we aren't aware of that needs to happen for the scene to happen. For instance, we didn't know that Joy would not invite you to play poker unless you'd already beaten Jennifer first. Everyone else played poker with Jennifer right away and so always got the invite from Joy as soon as it was timed. When one guy couldn't get it, we later found out why. I added this to the FAQ. If you find out why it's not happening for you, let us know and we'll add it.
As to the matter of customizing your character, you choose which stat you want to be good at and your name. There is a way to change your name after the first scene which darkhound1 posted a few pages back. Search here or my FAQ to find it. I don't see the value of more customization than that.
If you want to customize the MC's look so that he wears different clothes or looks more like you, then that's not going to happen. I am not the developer, but the question came up recently. It was suggest that the MC could have a slight build to start, buff in the middle and jacked when he hits 10 strength. This would have required 1200 renders just to get started, not to mention the 600-1800 renders for all the scenes he is in. Just count the times he is in Yvette's dinner scene. Changes at the core of the game are not going to happen because it affects everything else that has been built up to now. Sorry.