Why doesn't order (bootstrapv4) work?

Question

css

Why doesn't order bootstrap work and blocks stay in the same position as they were originally?

<div class="row">
            <div class="col-md-4  order-md-1">
                <div class="media af_spc">
                    <img class="align-self-start mr-3" src="img/icon/customize.png" alt="Generic placeholder image">
                    <div class="media-body">
                        <h5 class="mt-0">Accusan timar</h5>
                        <p class="h4block2">Sed ut perspiciatis unde omnis iste natus error sit voluptatem accusantium doloremque laudantiu</p>
                    </div>
                </div>
                <div class="media af_spc">
                    <img class="align-self-start mr-3" src="img/icon/time.png" alt="Generic placeholder image">
                    <div class="media-body">
                        <h5 class="mt-0">Accusan timar</h5>
                        <p class="h4block2">Sed ut perspiciatis unde omnis iste natus error sit voluptatem accusantium doloremque laudantiu</p>
                    </div>
                </div>
                <div class="media af_spc">
                    <img class="align-self-start mr-3" src="img/icon/music.png" alt="Generic placeholder image">
                    <div class="media-body">
                        <h5 class="mt-0">Accusan timar</h5>
                        <p class="h4block2">Sed ut perspiciatis unde omnis iste natus error sit voluptatem accusantium doloremque laudantiu</p>
                    </div>
                </div>
            </div>
            <div class="col-md-4 order-md-3">
                <img class="img-fluid img-rounded" src="img/phone.png">
            </div>
            <div class="col-md-4  order-md-2">
                <div class="media af_spc">
                    <img class="align-self-start mr-3" src="img/icon/support.png" alt="Generic placeholder image">
                    <div class="media-body">
                        <h5 class="mt-0">Accusan timar</h5>
                        <p class="h4block2">Sed ut perspiciatis unde omnis iste natus error sit voluptatem accusantium doloremque laudantiu</p>
                    </div>
                </div>
                <div class="media af_spc_a">
                    <img class="align-self-start mr-3" src="img/icon/send.png" alt="Generic placeholder image">
                    <div class="media-body">
                        <h5 class="mt-0">Accusan timar</h5>
                        <p class="h4block2">Sed ut perspiciatis unde omnis iste natus error sit voluptatem accusantium doloremque laudantiu</p>
                    </div>
                </div>
                <div class="media af_spc">
                    <img class="align-self-start mr-3" src="img/icon/camera.png" alt="Generic placeholder image">
                    <div class="media-body">
                        <h5 class="mt-0">Accusan timar</h5>
                        <p class="h4block2">Sed ut perspiciatis unde omnis iste natus error sit voluptatem accusantium doloremque laudantiu</p>
                    </div>
                </div>
            </div>
        </div>

Answer 1

in alpha 4 there are no such classes,
only
.flex-xx-first
.flex-xx-last
.flex-xx-unordered
https://v4-alpha.getbootstrap.com/layout/grid/#fle...
but in 4 beta
needed to connect this version
getbootstrap.com/docs/4.0/getting-started/download