In the wild it sometimes grows submerged in swampy evironments, so I would expect some melt and then It will grow. The submersed forum may be totally different than the emersed form. I likes shade too, so great for a low light tank. Let me know how it does, I might have to buy some soon.
Probably a few days. I'm guessing it will melt back like a crypt and then regrow. If I was you, I would pant most of it normally but save a small portion. I would hack the small piece so it was just roots and a little bit of stem and then plant it. Crypts grow better when you do that, I don't see why this plant wouldn't.