If you release a game for free does GPL still apply (using the exe)?

if so which resources have to made available?


Licence has nothing to do with money. It is a regulation how to use a product. (Like a drivers licence - it allows you to drive a car on public streets regardless how much money you spend or if you even have a car)

The ownership is still yours (unless you make it public domain).

All of them. As the Blenderplayer is already available via github, you just need to refer to the Blender web page.

How you provide the source that are not there (the .blend) is up to you. This can include that you send it via email on demand or it can be downloaded somewhere. With the GPL licence you commit yourself to provide it in an reasonable way.