Freegglers is a single-player game, but there's a plan for online co-op DLC in the future.
The game will be available for Windows and Mac. Linux is unsure, there are some technical obstacles at the moment.
Yes.
Yes, you can play using keyboard or gamepad.
GTX 770 should be sufficient.
Yes, there will be wallpapers for download in the future.
The price is not set yet.