I tried making 2 html files wich are identically the same but the only difference is the one is using the "story.js" and for the game slot 2 it is using "story2.js" but it's not working I thought it is using the "js" file to store the game... when I play the game in the game slot 2 and go back to game slot 1 they are on the same passage I left it.

Oh, I just found the solution to it...

I think you have to give the two files different story names. If I recall the save data uses a hash of the story name, so provided they are different you should be fine.

no need to change story name,
you need to change the squiffy.story.id in the story.js