Answeres to your questions:
1) There are guides on these forums to show you how to find what system revision you are on.
2)Yes you can play games from an external usb hdd,again there are guids for this.
3)2GB Sandisk sd card is recommended
5)You will have to do your homework!
Hope these answers help,a word of advice though through my own experience here it seems people dont like the same questions being asked over and over again (which is understandable).Read as many guides as possible that are relative to the subject you are interested in and place your questions in that respective thread.Also don't take advice from noobs as the lords gospel! ( i havent been here long but i have learnt that already) be patient and hopefully someone more knowledgeable like an Admin will answer your question.Remember knowledge is power so read,read,read.Just my advice take it or leave it.