0) You'll have to find one ...
1) youtube is OK (improved with Diablo)
2) don't play much (and no flash games)
3) linux only but it can be through VMWare Player and the already done SDK+Ubuntu image

N800 is fine
N810 has a better screen (outdoor viewing) a GPS (much more usable with AGPS-UI) and a keyboard but it is much more expensive and it is available ...

Fred