D
So, again, what I'm gathering from your illustration is that non-trinitarians are going to hell. Does this only include those who outright deny the trinity? E.g., those who study it and conclude it is a false doctrine. Or does it also include those who don't ever take a position on it for whatever reason? E.g., Those who purposefully choose not to take a position, or do not ever have time to study it out to come to a position, are never introduced to the concept, etc.
When I first became a believer, I was also established in the Catholic Church. Did the whole baptism, confession, communion, confirmation, and even became a godmother thing. I was raised in it, thus that's how I thought God was. And then, poof! One night I was in the audience watching Jesus Christ Superstar and asked God to let me know he was as real as the actor playing him on the stage. I woke up the next morning born again. (And to tie this all in, married to Jesus. Although, being raised Catholic that puts me at odds with what I was taught that meant growing up. lol)
I really was born again. That doesn't mean I knew Jesus like I do today. Never dawned on me to question baptizing babies, confession, communion, or confirmation for quite some time. (Godmother promises hit immediately, since I am my younger brother's godmother and our Mom was dying when I first got zapped by God.)
Was I not saved because I didn't change my mind on those things in a year? Two years? 5? 10? When is an important question. It's 44 years later, and I still don't know what I should think about baby baptism for sure.
BUT, that stuff really isn't important to salvation. Trinity is. It is an important doctrine to hold. Not to believe in the Trinity is not to believe in the Triune God. The God of the Bible. BUT (sorry, I like lots of "buts" lol), WHEN must one learn this about God?
Is that what you're asking? Definitely before death. (I don't see a way out of it, if you have enough time to study the Bible before you die. If you never learn about it, that's a different thing.) Outside of that, it really gets to the point of when are you going to study God to figure that one out? There was a guy on here a while ago from Africa who said he had never heard of the Trinity for the first two years he was a believer. Well, gee whiz! I hadn't heard of anything wrong with baby baptism until about 15 years ago, so I went with what I knew. God doesn't cross us off because we never knew some stuff. If that were true, we're back to no one is saved.
BUT he did hear. And then he had to learn it. And then he had to decide if he believed it. It all depends on our root structure. I have plants that don't need deep roots, but survive for years. (Decades, if you count my Prickly Pear Cacti.) So that whole thing about planting on rocky soil works for me. Easier to be planted in deep soil, but rocky is survivable sometimes. He didn't know, so God didn't count that against him. If he did know, didn't like that God, so went off to find one he does like, yeah! Seriously! A problem!
So, if you're asking me for a timetable on when to learn God is triune, got none. If you're asking if those who claim they are born again, but have studied the trinity and disagree? Yeah. They were never born again. God judges us on our talents. If we don't ever get that talent, he doesn't hold it against us. But he does not save people into believing in a false god.