CSS Laravel Bootstrap 4

I have problems with this new version and I have some things that if you are collecting the Bootstrap4 and others not.

For example, you are not able to teach these icons:

<a href="#" class="btn btn-danger"> <i class="fa fa-cog"          aria-hidden="true"></i></a>
<a href="#" class="btn btn-warning"><i class="fa fa-window-close" aria-hidden="true"></i></a>

Neither this one

    <section class="section-admin">
    <div class="panel panel-default">
        <div class="panel-heading">
            <h3 class="panel-tittle">@yield('title')</h3>
        </div>
        <div class="panel-body">
            @include('flash::message')
            @yield('content')
        </div>
    </div>
</section>

<footer class="admin-footer">
    <nav class="navbar navbar-default">
        <div class="containter-fluid">
            <div class="collapse navbar-collapse">
                <p class="navbar-text"> Todos los derechos reservados &copy {{ date('Y') }} </p>
                <p class="navbar-text navbar-right"><b>Deimos Castilla-La Mancha</b></p>
            </div>
        </div>
    </nav>
</footer>

however buttons like

<div class="form-group">
    {!! Form::submit('Registrar', ['class' => 'btn btn-primary']) !!}
</div> 

They work perfectly.