Embrace it, make the most of it. Anyone else’s criticism of you solely based on your age is frankly irrelevant IMO, and not worth even thinking about…

Lying about your age could be a problem in certain scenarios, like say some kind of medical situation, or even if a coworker expresses romantic interest with the belief that your age is something completely different. It’s not ideal, but I would probably suggest to tread carefully with it.

Don’t know the dynamics of your work assignment - however if you trust your manager it might be worth having a quick conversation about it to see if you can at least be put onto tasks that take your body’s condition into consideration.