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No problem! You can get a full image background by going to Dashboard > Appearance > Background and uploading one.

If you definitely want to create the theme from scratch, then I recommend that you build it as static pages first, using only html and css. Once you have all of the styling working properly, then you can move on and break it up into php files, replace body content with loop code, and header tags with template tags, etcetera. I always do it this way so that I can make sure my html and css is error-free before I introduce new elements, so I know that any problems need to be fixed for the WordPress output rather than the original layout, etcetera.

If you want plugin or functionality suggestions, I think you’ll have to be more specific about what each functionality piece needs to DO. I suggest browsing the plugin directory first, though, so you have a sense of what is out there.

Your theme is a premium theme, so we can’t look at it to see for sure (this forum can only support wp.org repository themes), but I believe there is an Advanced Theme Options panel that comes with your theme. That may include the ability to change the footer colour, but it might not. If you don’t know for sure, you should ask your theme developer. (I think support is here)

The non-support way to make these changes yourself, however, go like follows. To change the colour, you just need to make a small change to the css styles.

a) Either you can download a custom css plugin and make the css changes that way. (here are some options for plugins)

b) or you can create a child theme (very important! avoid editing the original parent theme files!), and add the adjusted code to your style.css file.

Here’s the area of the css that needs changing:

#footer {
    background: none repeat scroll 0 0 #666666;
    border-color: #666666;
    border-style: solid;
    border-width: 1px;
}

So if you follow the above steps and then change the background colour from #666666 to another colour value, you’ll be set!

I haven’t tried these, but I see some options:
Customer Area
SP Client Document Manager

Let us know what you find that works for you!

Rewind posts is not necessary when you’re using new WP_Query() because it creates a new standalone query object. (i.e. it exists outside of the main query object, so the main one never ran and no rewinding is necessary)

This wouldn’t be the right use of rewind_posts() regardless – you have to follow up rewind_posts() with a new query every time so that you can start at the beginning.

The straightforward way to do this would be to create a new query object for each little category set you want to run.

<?php
    $category12 = new WP_Query();
    $category12 ->query('cat=12&showposts=2');?>
<?php while ($category12 ->have_posts()) : $original ->the_post(); ?>
<!--content-->
<?php } ?>
<?php endwhile; ?>

<?php
    $category13 = new WP_Query();
    $category13 ->query('cat=13&showposts=2');?>
<?php while ($category13 ->have_posts()) : $original ->the_post(); ?>
<!--content-->
<?php } ?>
<?php endwhile; ?>

etcetera...

Could you provide the url so we can check it out?

That’s a long list! You obviously have the drive to get into it, so I’m sure that you’ll familiarize yourself with the WordPress environment quickly. My advice would be to start as simply as you can, and try to work up a demo without getting too far into functionality.

Have you found this section of the site yet? WordPress Lessons

The first thing you should understand is that all styling and layout (and some functionality, depending) is controlled by themes. This separates presentation from data (all your posts, pages, users, attachments, etcetera), which is great for experimenting and customizing. Themes can be applied to the site, replaced, switched, adjusted, etcetera, to display your data, but all your data remains unchanged.

You can find free, reliable, recommended WordPress themes in the theme repository here. Take some time to browse: if there is a theme already built that bears any structural resemblance to the design that your team has put together, then you’re halfway there already!

If you search the themes using the tag filter here, then you can narrow down to ONLY responsive themes by selecting ‘flexible-width.’

The next step is to make a child theme, and apply any design changes you need to it. This way, you have the underlying reliability of the parent theme, which will benefit from future updates by the developer, while still controlling all the things you need to customize. You may have to edit template files (php), or you may be able to do most of it by adjusting the css – it all depends on how far your parent theme design is from your desired design.

Login and user profiles (and user roles, from admin down to subscriber) are standard features in WordPress. If you need to do more than what is ‘in the box,’ you can browse the many, many plugins that deal with user accounts, roles, permissions, display, etc. There are also many plugins out there for advanced search and ratings and forums.

There is new media player functionality in WP 3.6 AND there are many other players out there. I can’t comment on specifics without more details about what you want, where the media content is coming from, what services you may be using, etcetera.

You’ll find there are tons of options and resources for you to do the things you want to do, so really don’t worry – but I’m sure it feels like a giant crazy list right now so I really recommend you start at the beginning and get a handle on the theme creation and styling itself, then add functionality in pieces, one at a time. Best of luck! Check back in when you need to.