A:
1) I don't think it works without the proprietary USB dongle
2) Yes, you can adjust the brightness, sound, and other Mac features. Including laughing mission control.
3) Battery life is Great! I never have any issues with the solar panels not fully recharging the batteries.
4) I've only had my new keyboard for about 6 weeks. So far, I've not had to change any batteries. And from the way it is working, it won't need any battery changes any time soon. I've never ran out of power. The Solar panels keep the batteries charged all the time