The (J) save for Picross is a bit messed up for the (E) release. It switches the progress of normal and free modes. So, if you had everything open in normal, but only the first 4 in free, when you use the (J) save, normal will only have 4, yet free will have everything open. All the puzzles will still be solved, too, but it seems you'll have to play them again to make the game "remember" that you did, and open the rest of the levels. All other progress will be there too, like unlocked daily picross modes, and downloaded packs. I've tried a bunch of things, but I can't get the save to convert properly.
Seems fine to me, did a puzzle, switched it off and on again and it said something about fixing the save cos it had become corrupted. After that it was fine and all my progress was same as before.