you can pretty much do anything with the device, with that said, anything you do to your device can "break" it as in you have to start from scratch. its A LOT more forgiving than other platforms as its very hard to brick. but with that said, as long as youre willing to do the research, and have patience, a key is investigation, a lot of ppl have tried a lot of things, so you can work from the mistakes already made.

as for your questions:

1) yes, flashtweakr (beta application)
2) yes, but not full versions (all working components) of those two OS'
3) yes, but there are several different meanings to your sentence, so i cant be certain about what your asking specifically. but there are caveats to each answer. for the most part it is possible, regardless of your questions meaning.
4) no, your out of range of the router. you can use the 2G/3G once that happens --* i stand corrected above!! and will look into this
5) yes, there are other applications for music on the device, but they all use pulseaudio which is the audio controller
6) we are in year two (nov '09) was the release. no more planned OS upgrades (maybe one more, but its doubtful) focus is on MeeGo
7) yes, youd have to search for them i dont know any off the top.

enjoi your device, still one of the best out.