You don't. You use Google Docs instead. You cannot load any native Windows applications. You must use cloud/web based applications or apps that were specifically designed for the Chrome OS.

Google is claiming the battery lasts 6.5 hours:
http://www.google.com/intl/en/chrome/devices/landing.html

Reviewers are saying that's not true....

It lasts much longer:
http://www.zdnet.com/review-the-arm-powered-samsung-chromebook-7000006097/

Yes since Google Chrome comes with Flash pre-installed in it's versions.

iTunes cannot be installed on a Chromebook. You can however upload your iTunes collection to a cloud-based music service like Google Music or Amazon Music and then stream your music from there to any device you own.

You will be able to connect to the Mi-Fi as a normal connection without any problems, just as if you are on the go. As for the printer you will need to check if it is a compatible cloud printer. But if it is not a cloud printer you can connect it to your other computer and use google cloud print to connect it. This will allow wireless printing.

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How is your desktop connected today? If you don't have a wireless router today and wish to use both the Chromebook and desktop at the same time, I think you'll be best off purchasing a Wireless router. Take a look at a low-end Linksys or Netgear unit, you don't need anything overly fast since the Internet connection will be the biggest bottleneck.

If you don't want to go wireless, The $249 Chromebook does not include a Ethernet port but you can purchase a USB to Ethernet adapter.

Yes, all websites that are not specifically designed for Internet Explorer or require a proprietary plugin like Java will work great with a Chromebook. Yahoo develops their website towards web standards so things like Yahoo mail should work perfectly.