Well, IE10 will be backported to Windows 7, and it may rely on some of these features (it certainly relies on other Win8-specific things), so I'd expect some of them might be.
They are tied to one device at a time, but you can move your "account" to a new device (you can't use the old device with it after that, though).
And you can redownload games.
I think Nintendo's real problem with the DS is that people see it as a device solely for young children - the software selection doesn't exactly help.
They need more FPSes, I think. There are plenty of people who grew up with Nintendo who'll want to play Zelda and Mario again (and they can...
I think you're wrong on this. It's actually ahead of its time - new web technologies haven't yet matured.
The era of browser apps and games is nearing, but we're not quite there yet.
Windows on ARM is just an ARM port of Windows. The Windows API is still there, after all, Microsoft's own apps rely on it. Heck, the Metro UI and APIs are built on top of it.
Firefox will work fine.
You're wrong too I'm afraid. It isn't a true browser. It receives a super-compressed proprietary format "page" from Opera's servers.
What you're thinking of is Opera Turbo.