1. You can but you need to load the 205 with a tcx, course, file. Bikeroute toaster can do this but I think you'll be limited for way/route points.
2. Yes.
3. Of the three I owned I never got over nine hours life. I resorted to an external battery pack connected with a USB cable.
On the whole I recommend the Edge 605 as it has maps, can handle gpx files, better screen, better battery life, I've done 12 1/2 hours and a friend has tested his 705 to 15 hours.