I have beat the game, I got the Hero's crest thing, and entered the portal, beat the final boss and saved over the same save file.
Then found out that the Hero's crest opens a gate in the noise dunes. But I can't go back since I saved after beating the final boss.
So I though about getting to noise dunes by playing the second playthrough. But I heard you can only open the Hero's Gate during the first playthrough. Does that mean I have to start a new game? Then why do I begin the second playthrough with the Hero Crest item?
By the way, what does a second/third/fourth playthrough offer anyway?