For the purpose of cleaning, I need an aggressive solvent for cured or partially cured resin that will degrade resin down to its liquid state. I'm looking for one that would eat out specifically resin (I'm using regular Anycubic green resin) in a rapid fashion but would leave painted / metallic parts and screen of my 3D printer without damage.
Concentrated nitric acid will remove all organics, including your skin, wire insulation, etc. It will work on a glass plate, but the fumes would eventually damage the plastics on your printer unless you remove the glass plate to clean it. Nitric acid will destroy most build surfaces that are added to glass. To a lesser extent concentrated sulfuric acid works, but it tends to leave carbon behind. With these acids it takes special gloves, and I would not even depend too heavily on them always working. The more concentrated the acids (the less water), the less they will attack metals. Note: this will quickly strip the paint off metal parts.
Thus, you probably cannot find an aggressive chemical that is practical for you to use.
Returning is impossible
Resin does not just harden, it polymerizes into shape from monomers in a chemical reaction. That means to break it down, you need to destroy the whole chemistry. There is no solvent that can simply reverse it.
Wiping is easy
As long as the rein is still liquid, you can wipe it off. Then clean the parts with Isopropylic alcohol.
Destroying Resin-Polymers is incredibly hard for most solvents. The most simple solution is usually oddly enough to use physical force. Resins are super brittle and chip off, but might damage the paint coat in the worst case.
If you can, you might put your printer in a cold environment and see the resin gaining cracks, as it shrinks slower and less than the metal. Then, putting it back into the heat adds more.
I would try hexane, and then Dichloromethane and if those did not work, I would heat up sodium hydroxide to about 70-90 °C. These would work better if you print in PLA resin, it's available from a few sources now.
Bucktown polymers and 3Dresyns both have a water-soluble resin. You could also print, make a soft silicone mold, cast in chocolate or isomalt and quickly seal in b72 enamel to hold its shape for your next step.
Another great option is to cast the printed mold with Amazing Remelt as you can microwave it out of your shell afterward. Or heat up/steam.