cichooocki on "Building one-page portfolio with additional image gallery [bootstrap]"

I'm creating a custom theme with bootstrap that will be used by a photographer and I'm trying to integrate it with wordpress. My main page is in the one-page style and has following sections:
- cover image with page title and description
- about me section
- portfolio with 6 exemplary photos and link to full gallery
- contact form

"About me" content can be edited in the admin panel (I created a separate "about me" page and linked up its ID with the section), portfolio photos are the feature images of the latest posts.
Navbar consists of sections titles as well as link to gallery.

And here are my questions and problems that I need to solve:

1) How can I add a functionality to edit the cover image from the admin panel?

2) What is the best way to create a separate gallery?
I thought about categorizing the posts with "gallery" and "portfolio" when all of the first ones would be posted in gallery, but also some of them would be featured on the home page in portfolio section.
Is it a good way to do that? How can it be achieved in code? Here is how the portfolio code looks like at the moment:

<div class="row"> <?php $i = 1; if ( have_posts() ) : while ( have_posts() ) : the_post(); ?> <div class="col-sm-4 portfolio-item"> <a href="#portfolioModal<?php echo $i; ?>" class="portfolio-link" data-toggle="modal"> <div class="caption"> <div class="caption-content"> <i class="fa fa-search-plus fa-3x"></i> </div> </div> <?php the_post_thumbnail( 'full', array('class' => 'img-responsive') ); ?> </a> </div> <?php $i++; ?> <?php endwhile; endif; ?>

It publishes all of the featured photos of the posts in the portfolio section.

3) What is the best way to create a separate gallery in my case?
Should I create the "gallery.php" file with all of the code and link it up in navbar? What should be the link destination in navbar that would lead to the gallery?