First of all thank you for your feedback and for playing the game.
I tried to implement a saving system, but for some reason i though i would be easy and leave it to the end, the result was that it broke the game, it was the last day of the jam so i took that out, i should try to implement that in the future.
I was thinking of adding a sign in the cell, that told you the controls, and having like a puzzle where you must have use the duplication ability to get out of the cell, but i leaved it at the end and ended up having no time to do it.
About the combat, in retrospective, the switching characters mechanic was a mistake, but i realized that too late, and scrap that mean rethink everything i had done at that point, that was a week ago, i though of adding to the duplication the ability to explote so when you only have that character you could still defend yourself and maybe even block bullets, but that would make the combat more awkward.
I also though about adding a bar in the ui that changed the the position depending of what character you are controlling, but i was terrified to mess up the ui beacuse i wasted 7 days making it work properly, so i leave that at the end and ended up not doing it.
About the store you can only purchase 3 potions, you have to use at least one to be able to buy again, i should have added a way of making the player know that.
But well at the end i'm glad i was able to make something, even if it's not perfect, i'll try to make an update to add the things you mentioned and really apreciate your final advice, i'll have that in mind when i design any game that i do in the future.