Autistic adult here:

I do feel like I have a more childlike appearance sometimes, less so in recent years. I think that because of the seriously messy place my mind was in from the very start, it took me longer to interact with other people enough to develop the social awareness I needed to “fit in”, and not “fitting in” is often equated with being childlike, IMO. I still occasionally mutter to myself in public, have odd movements and posture, and generally act in a way that diverges from the social norms of the people around me, for better or for worse. Medication has changed all this around in ways that are too complicated to get into in one comment.

My mind never stopped developing. My brain chemistry changed as I went through puberty, and then through adulthood when the prefrontal cortex starts doing its thing. I kept gaining new knowledge from my surroundings and my peers and that changed how I thought about things on a basic level. There are certain specific areas in which I was always considered “more mature”.

My experience doesn’t necessarily reflect those of other autistic people who’ve had different hands dealt to them. I’d be happy to answer any other questions you have.

To quote the words of the Behind the Bastards podcast, I think you should make it absolutely priority #1 to get your condition treated and prevent yourself from committing sex crimes, as in, it should be a slightly higher priority than breathing