Just to answer the hypothetical of someone being forcibly transitioned by their parents as an infant, there is actually a precedent for this. Quite a few really, though I don't have concrete numbers.
For one specific incident we can look at the story of David Reimer.
There's a lot of nasty stuff in the story, but the cliffnotes version is that due to a botched circumcision at birth, the doctors surgically altered him to present as female, and he was then raised as a girl, given estrogen during puberty and so on. I get the impression this was standard practice at the time if the doctor's accidentally chopped a baby's penis off. He was told about these circumstances and surgically and hormonally transitioned back to male at the age of fourteen.
As for how things were going in his brain during all this? Hard to say, the doctor, who saw this as a chance to determine if gender was learned or innate, studying him and his twin brother through the whole thing was far from good at his job, and was acting with little to no proper oversight, and essentially molested the two boys. His study claimed David was identifying as a girl, but his judgement was suspect at best. There's probably little to actually learn from the case other than that children aren't lab rats.
David and his brother both eventually committed suicide at different times and in different ways. Not the only case of this sort of thing happening, but the one that I can most easily recall and find stuff about.
More broadly, 'corrective' surgical intervention on the genitals of newborns wasn't exactly an uncommon surgical practice in the recent past, fortunately a lot less common now to my knowledge. Children born with genitalia that didn't match their genes, who had ambiguous genitalia or who were otherwise abnormal in that regard were usually surgically altered according to what was most convenient to do with what genitalia they had and given hormones to make them externally present as their assigned gender. Micropenises turned into vaginas, penis/vagina combinations turned into whichever it already most resembled, that sort of thing. Not super clear on the specifics tbh, I just know it was done with the good but misguided intentions to allow the child to live a 'normal' life.
It was part of the 'gender is entirely learned' school of psychology. Much like the studies that wanted to determine if 'being human' was learned or innate it was filled with really sketchy practices, and gleaned very little actual information due to poor methodology and low sample sizes. The theory went that if you raised a boy as a girl, they would be a girl, no internal biology would be prodding them and saying 'but we're a boy.' Applied in reverse as well.
It was a very simple theory, and a very simple view of gender. Like it was an on/off switch. Two options, no sliding scales, no nuance. Simple, easy, convenient. Lazy really.
I don't know if David Reimer suspected something was off before he was told about the whole 'whoops, we cut your dick off as a baby,' thing and transitioned, but I imagine on some level he must have. In theory a modern Reimer might just identify as a transman even before being told he was more accurately amab. There might be studies on intersex and reassigned at birth people that could shed some light on that, and they might be informative to some extent about trans people.
Fun fact: As I recall I first learned about the whole surgically altering babies genitals things from a Ripley's Believe it or Not! book my brother and I had as kids, which had a page about an intersex person who had transitioned to the opposite gender from the one they were assigned at birth as an adult. Might be misremembering, but it was one of many, many things I learned about as a kid that gave me a dim view on the medical practices of the recent past.