I don't know why you decided to put all the first-sex scenes of the girls with an unprotected/raw sex scene, then later the characters use a condom in the following scenes... I'm not sure if it bothers other people, but for me, it kinda ruins the "progressive corruption" aspect of the story. HC2 was better in this part.
Imo, a good sequence of sex events for a Corruption story should be:
Groping stuff scenes > Non-penetration sex scenes > Condom sex > Unprotected sex > Creampie > Anal (anal scenes being optionally before or after the raw sex scenes).
I wouldn't necessarily say that it's a good sequence but it is definitely the most commonly used one in corruption based games, however in HC3's case every character had a good reason for why they did not use protection during their first time, and it's simply because of the situation they were in prior to losing their virginities. Cyanna thought that she was going to die and Rose was JUST informed that both Leto and Cyanna would most likely die before sunrise unless she prevents it from happening, when you're in that position the threat of getting pregnant is pretty low on your list of priorities, i mean what's the harm in a creampie when you're gonna be dead by this time tomorrow ?
LMAO also imagine, the love of your life could die in any moment and you're rummaging through the Duke's drawers looking for a condom so that you can have sex that's gonna potentially save his life.
As for the side characters, i'm pretty sure Jazon and Haylen DID use a condom for their first time, and Lily...well, i feel like it's pretty self explanatory but at the same time i find it hard to actually explain. So basically, while Lily was giving Nezar a blowjob she was debating whether or not she's gonna actually go through with her plan and allow Nezar to have sex with her, however when she noticed that Nezar was about to cum she made the decision unconsciously and when Lily realised WHY she stopped blowing him, she got infuriated by the idea that she actually wants this, she then shoved Nezar onto the bed out of anger, and then she sat on him in a heat of the moment and started fucking him. Basically she was too angry to think about trivial things such as condoms, and Nezar would've been a fool to warn her, he was just there for the ride...literally.
The game still follows the same sequence that you just mentioned and i know that you noticed it cause you said it yourself, every sex scene that involves any one of the 4 main girls is done with a condom on with the exception of each girl's first time, but in Rose and Cyanna's case those first times happened under special circumstances that actually allowed the sex to happen, if they would've been in a safe enviroment where they had time to think about using protection, neither of them actually would've even considered having sex in the first place.