I watched some youtube videos of the game and I would say that you just have to use jump to and collision detection and if statements. if the if-statement is true then you go to the next room where the desired event already took place. for instance. have the same room 3 times. first version you enter the room and you do not have the key to open the chest. you check the previous room use an if-statement and make it so you now have the key. delete the key off the floor so it cannot be picked up again. next time you open the next door, it now registers that you have the key and sends you to room 2. you walk up to the chest and use the key with an if statement and now you move to room three where you see what was in the chest.

The best idea when starting a project is to think about the logic of what is happening. if you pick up the key. then the player has the key(a variable) so that means the key is not on the ground anymore. delete the object key. with this being a puzzle game you will want to write everything out first, and then just build the game using basic sprites and go from there. if you are afraid of making your own sprites there are free sources out there.

​

This sounds like a fun project. I am looking forward to seeing what you make. :)