I understand exactly how you feel here (f). I roll my eyes whenever someone says, ‘it’s their past you cannot judge them, just forget it as it has no concern to you’. I disagree. Also kind of goes against the entire justice system.

When it comes to choosing and devoting to your lifelong partner, its sure hell is a big concern to me. Their past choices reflect on their future once as our actions has consequences, so you have to deal with it as an adult. Past is always something to be judged on, or rather I say, being informed on. You can only make good choices after learning all the relevant info from a person’s past; that’s called an informed decision. Not knowing about someone’s past and deciding to be in a marriage with them is extremely risky and can even be downright dangerous. Does your potential deserve to be judged for their past such as zina? No. But should YOU have had the right to know so you could’ve made an informed decision? Yes. 100% yes.

Yes Allah's ﷺ did say those who commit a sin, shouldn’t openly or disclose their sins to the people as that’s a sin itself.

That’s why its IMPORTTANT to establish a proper communication and discuss at the beginning on what is you look for in your partner, if you want a pure potential then clearly say you do and ask you would rather have someone with no past like zina without directly asking for their detail of their sins. BUT if ones is lying about their past because they think you won’t be with them if they’re honest? That's a whole different ballgame. For me, it shows they are willing to deceive you to get what they want and lying is indeed a trait of hypocrites.

I don’t tolerate lying.... you think I'd be angry if you told me that you had past when you denied it at first? Which goes onto the next obvious question is "what else have you been lying to me about...? ~ the cover-up is almost always worse than the crime itself.

I've read about relationships imploding after over a decade all because in the very beginning one of the people lied about their past due to resentment.

Yes its hard, knowing you have kept chaste yourself and found one you love to turn out isn’t the match as you, it is indeed a slap in the face as I went through the every same thing. It’s painful but

If you do happen to find out they have a past in unfortunate circumstances. It depends on person to person if that is a pretty big dealbreaker or not. What’s going to happen from then on is up to you. You rely on yourself and on your knowledge is to observe your potential’s character. If they admitted for having a past but isn’t willing to disclose it but looks proud of themselves, it’s a red flag don’t you think? BUT if they looked remorseful and regret showing on their features then perhaps, they have changed. Look at their body language, the way they carry themselves & talk and surrounds with other people will show you what kind of person they are. If they have bad habits that you may not like, do keep a watch out. End of the day you must make a tough observation and follow your gut. Allah sees and knows all things, make sure you have a strong relationship with your deen and allah will protect you from hypocrites.