Do I need several installations of WordPress?

I am so pleased with WordPress! It is so easy to set up pages with navigation and tabs. In addition, I have a three column theme where I can offer all kinds of images with links for every page.

My question is:

1. I want to have like eight tabs at the top of my site – for one language (English). And then eight different tabs for my site in a different language. Now to accomplish this, do I need two different installations of WordPress? Do I need two different domain names?

2. I would like some of my pages available to the general public, and some pages for members only. I could do this through a password for all of these pages. But wouldn’t this be unpleasant for the visitor to constantly be entering a password every time he switches pages.

Would it be wise to have a different installation of WordPress: one for members and one for non-members?

Would I end up with four installations of WordPress???

If you make it this far, I thank you for taking the time to read my whole book!!!