Your right, credit for the microscope falls to 1590, Hooke improved the design, still far beyond where we are in mythic Europe. Your wiki source is not an academic source and only sites one book for your Chinese water microscope, I have found no other academic references, so it's not a valid resource. Though glass that could magnify things was invented (a magnifying glass), they are not microscopes. But if we are going off the premise of what "has been" invented in the period, I should be able to have all the cannons and rockets I want, as the Mongols have a cannon, and the Chinese have invented rockets. But that isn't what was in Europe. China was closed off and it's not like you had a way to share academic progress around the world. Technology was at a near stand still in Europe. This is one of the reasons we all it the dark ages.
The term Metabolism refers to the biological cellular function. Something unknown until the development of cell theory. Defiantly not in the dark ages. Most medicine and healing of injuries was based off balancing the humors. Inflammation would be cured through bleeding for instance. Disease was caused by demons or imbalances in humors.
Making a blossom out of season in a moment is under rego yes, but to make it stay that way would require vis, otherwise the spell only lasts as long as it's duration. Then reverts to its original state. Also, Brutus, bringing someone to maturity over night is CrCo not Rego. This fits the hermetic model that you reach your most perfect form at maturity. Than you degrade away from that with age, predo.
Now you are saying that you will heal by making something that will occur in the future happen in the present, so thereby effecting something that will happen the the future, This is in violation of the limit of time. We have now violated 3 of the limits of magic and are using Rego to age, which you cannot do, and making an effect permanent that makes something better (creo) without vis. Show me where you can heal with rego under the descriptions of the arts. The descriptions are pretty clear that creo is the only healing art. aging is not a side effects, aging is the effect, you are causing time to pass faster for the person, that falls under predo, which does not heal. Bane of the decrepit body ages you 5 years, but you don't get healing roles. If you want to call it a side effect, why can't I just muto their head to fall off and then they die as a side effect. Even turning someone to stone does not kill them. This completely ignoring the underpinnings of magic in order to make these spells work. Which is the idea of the prefect form and essential nature. Aging takes you away from your perfect form. Another example is under the same idea I could rego someone into eternal youth, stopping their body energy, or kill them the same way. I'm just slowing the bodies processes and thus I don't need longevity potion or to make aging roles ever. But again, I'd be ignoring the limits of magic.
Having someone heal faster is already under creo, that's what the instant healing is and giving bonuses does in effect.
If you want to do this for your game, that's great! More power to you. But justifying it into the hermetic model, the rules, the cannon. It's not going to fit at all. Again, show me anywhere in the books that rego can heal and that is not strictly a purview of creo. I cannot see rego working this way with anything short of a hermetic breakthrough.