that game with the numbers and red squares... I knew how to play it, but I didn't get the right answer. I even got to the walkthrough, and it was the same result, it doesn't work.
to use potion, you must have the potions on inventory. Most likely is that you have all your potions on Mardek, because that other characters can't use them as they don't have them.
reason why the saves don't work is below your comments:
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I noticed this game doesn’t even create a save file in the cache folders on your computer like the other ones do. Who knows why, but that’s definitely why your stuff is gone after you go away from this page."