First of all for the fiddles you need to add the scripts as well, from resources in the side panel
You simply need to call the player as
this.player since this is the way you have created it. There is nothing defined as
player in your code.
For the coins, stars, fly through do you mean through the world bounds. If so make the collide with the world bounds:
star.setCollideWorldBounds(true); inside the
stars.children.iterate you have written. Also there may be a way to do this with the group,
stars for convenience. Not sure about those currently. But if you bound the bottom of the world by putting a ground platform which you set to collide with stars then you will not need this. Stars will hit the ground and not fly through. I guess you have some problem with placement or creation of your platforms but I do not know what ii is?
In the fiddle could not see you star assets.
Also the assets cannot be found anymore in the fiddle, naturally, you can add their phaser labs address if you want the assets in the official tutorial. Pattern like https://labs.phaser.io/src/games/firstgame/assets/dude.png.