So after more reading, the formalin is a longshot but it’s worth it. What it’s supposed to do I think is prevent even worse damage that occurs during thawing. Then it can be stored and observed at room temp with hopefully minimal damage. There will be damage from freezing but the thawing is what will really ruin the tissue.
The problem is, fixing something as large as an entire frog in formalin. It sounds like it’s possible but will take longer to penetrate.