Let me try and answer each of your 3 questions:
- In dev mode you can hit ctrl+alt+T and get the shell. However, it's a trim/secure shell that won't let you do what you wish...
- You can load any type of OS from usb and install it. I have few friends that did it with ubuntu but each and everyone of them - moved back to chromeOS... may be, in your case it will be different :)
- Cloud9 is a cloud IDE that give you ability to develop in Python.
You can read a blog post I wrote in the past about 'developers and chromebook' - http://greenido.wordpress.com/2011/07/04/web-developers-and-the-new-chromebook/
Good luck!
