What are the skills and knowledge you could actually bring & fully realize at some point in the past?
And we're taking this in the strictest, nerdiest, materialist lense. I don't care how smart you are you ain't making a steam engine the in bronze age, for instance.
So what could you create, with just your knowledge & period tools? What kind of institutional, technological, philosophical innovations could you realistically recreate? How would you interface with the social fabric of society to not be some crazed pariah who never positively influences the place they went?
I'd argue it's in the sense of da vincis first helicopter in that it's like a fun novelty thing that wouldn't get realized much, much later as anything but.
It's sort of a pareto principle thing where 80% of a bicycle is pretty easy to manufacture out of whatever you have lying around and the 20% get nigh impossible without fairly advanced metallurgy I think.
A Balance bike or something like Karl Draisine's dandy horse is feasible much earlier than it was invented, sure, but that was and would always be a rich people toy since it has very little use other than going zoom zoom for fun.
Sure, frame, wheels and such, sorted, someone just needed to put it together in like bicycle shape or thereabouts.
Drivetrains get pretty complicated though, unless you penny-farthing it you're gonna need a chain of some sort or it's just gonna be a novelty again. Sure you could do like leather band around wooden sprockets or some shit but you're gonna be replacing these so often and they'd require so much craftsmanship you're back to rich people toy. Without ball bearings and such it's also gonna be a such a slog to ride it's going to be pointless.
Once metallurgy is there, though, you could kickstart the fuck out of modern bicycle design by just "inventing" it and a load of other shit that was entirely doable way earlier. People were fucking around for a while there.