Stick multiple posts in a single category

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Your category.php should have two loops — one for stickies, one for regular posts:

<?php
// get sticky posts array
$sticky = get_option('sticky_posts');

// First WP_Query arguments
$args = array(
    // include stickies
    'post__in'  => $sticky
);

$query = new WP_Query( $args );

// First loop for stickies only
if ( $query->have_posts() ) : while ( $query->have_posts() ) : $query->the_post() );

    echo get_the_title() . '<br />';
    echo get_the_content() . '<br />';

endwhile; endif;

wp_reset_postdata(); // don't forget to reset before the next loop

/***************************************/

// Second WP_Query arguments
$args = array(
    // exclude stickies
    'post__not_in' => $sticky
);

$query = new WP_Query( $args );

// Second loop for posts excluding stickies
if ( $query->have_posts() ) : while ( $query->have_posts() ) : $query->the_post() );

    echo get_the_title() . '<br />';
    echo get_the_content() . '<br />';

endwhile; endif;

wp_reset_postdata(); // if necessary

More than likely, you will need a lot of additional WP_Query parameters.