Aged naturally… to play both older and younger… within a single film…

Given how most films only take a few months to film at most, I don’t think natural aging will have enough impact on a character to have a distinct “younger and older”. If the film took years to make, then parts would seem really low quality compared to other parts. If the character was only a few weeks older, you wouldn’t notice the difference between the accurate age and the reshoots.