<div class="container">
    <header>
        <div class="row">
            <div class="hidden-xs hidden-sm col-lg-12 menu-desktop">
                1 2 3
            </div>
            <div class="hidden-md hidden-lg col-lg-12 menu-mobile" >
                4 5 6
            </div>
        </div>
    </header>
</div>