if anyone can help me with the following it would be much appreciated.

I need to know if Wordpress can perform CMS for a website in the following capacity:

1. back-end login area for multiple users accessible from the main site.
2. a page where files can be uploaded to and then downloaded from, which can be archived into info like date added etc. to be used by a search feature.
3. each upload can have it's own blog where clients can discuss that particular file.

and not so importantly:

4. can the design of wordpress pages be completely customized.

Any help would be great, thanks.