I've had that feeling of envy a lot lately. Particularly towards very young girls, because it kills me that no matter what I do, I'll never be able to experience that time in my life as female. Teen and older... I dunno, I feel like to a degree I can have similar experiences moving forward as teens do. Certainly I'm going to have the awkwardness of a first date, kiss, or more as a girl. I still have time to learn to do things I missed out, and so forth. But nothing, absolutely nothing, can turn back the clock on innocence(or simply mental development), and enable me to have those true childhood experiences. I don't even know if it would have been all that different in terms of what toys I played with or who my friends were, but nonetheless when I see pictures of my sister from that age, I can't help but feel that pang of loss.
(Though the worst bit of jealousy will always be never being able to be pregnant. I don't tend to be triggered by much, but the one thing that gets me every time is when I see people say "[Trans girls] are lucky they don't have to deal with periods". I don't see that as lucky in the slightest, I see it as though there's a knife in my gut I can never remove, and casual dismissal of it is just a twist of that knife. Wow, I'm cheery today.)