The game logic costs about 0.07 ms per tick. The strip redraws ten times a second by default, twenty while you work so damage numbers float smoothly, and 30 during fights and chest openings. In very heavy scenes you can turn animation or damage numbers off in the preferences; the strip then refreshes every few seconds and still animates fights and chests.

No. The game never writes to your scene or your undo history. Its buttons are internal operators and don't create undo steps.

Leaving it open idle earns only the slower miner rate. Closing it earns nothing, and a frozen or sleeping computer earns nothing either. The game is built to reward actual work.

No. It only notes that some work happened, not what it was. There is no network access, and the save is a small local JSON file.

No. Only one copy of Blender plays at a time; the others show a read-only view of your progress. Several windows in the same Blender share one game.