Yes, you can hack and use mods with the official version of MW2 just as well.
I don't do it because I don't want to risk getting my (expensive) copy of MW2 banned.
As stated above, AlterIWNET is the (illegal) cracked version of MW2, which uses it's own servers instead of the official IWNET.
People use alterIWNET for several reasons; The main reason is because it allows you to play the game and the new DLC's for free (albeit illegal).
Furthermore, alterIWNEt is used by ppl who want to use mods and/or cheats without risking getting an expensive game banned, to avoid the often laggy IWNET, host and control their own 'server', etc.
When a game gets updated to a new version, most hacks that were made for previous versions won't work anymore.. The hack's creators usually update them rather quickly tho.
Use LoaderX. Instructions can be read there.
Many mod release posts have detailed instructions, like Terminator Invasion.
I assume you mean console as in developer's game console and not as in xbox and PS console?
The dev console is unlocked by default when using alterIWNET.
For the official version of MW2 you'll need a tool that unlocks the console, such as VAC chaos (could very likely get you banned, use at own risk)