[eluser]Tom Glover[/eluser]
Welcome to the Forums,
1. ACL is controlled by a third party library, you will find these in ignited code. Redux Auth and BackEnd Pro are your best bets.
2. you can use routes to determine what language people are viewing the site.(if this is what you mean) There are many post about this in the forum so have a look around.
3. Have a Look at BackEnd Pro again.
4. Hooks are described in user guide, for more help on the topic ask with more detail in what you need to hook and why, then some one can help.
5. Up to you, how ever you code the BackEnd or features will determine how it is updated.
6. You can write your own search engine, there are a couple of libs in the ignited code section to do this.
7. Have a look in the Wiki at RSS and Social Networking, bot of these explain the rss side of CI.
Hope this helps you.
TJ