No, it's an isolated web game with no blockchain interactivity. The in-game currency, although called $DOBO, is not the real DogeBonk crypto asset. You will not earn any crypto asset(s) by playing this game.
It's only me in my spare time.
No, but BattleBonk is PWA compatible. This means it can be installed on mobile devices for offline play and also becomes fullscreen playable on most platforms. To test if this option is available for your device, navigate to the Game page and if your device supports PWA then something similar to the screenshots below should present.
No, I don't have the experience to implement this; it would be too difficult, and introduce too many security concerns.
An online scoreboard is a current development focus.
It's a small project, and software development is a hobby of mine so what little money it costs, it is well spent. I'm not taking donations, but thanks for the thought! Share the game on social media if you can though :)