Bootstrap 3: pull-right for col-lg only

Try this LESS snippet (It's created from the examples above & the media query mixins in grid.less).

@media (min-width: @screen-sm-min) {
.pull-right-sm {
  float: right;
}
}
@media (min-width: @screen-md-min) {
.pull-right-md {
  float: right;
}
}
@media (min-width: @screen-lg-min) {
.pull-right-lg {
  float: right;
}
}

.pull-right-not-xs, .pull-right-not-sm, .pull-right-not-md, .pull-right-not-lg{
    float: right;
}

.pull-left-not-xs, .pull-left-not-sm, .pull-left-not-md, .pull-left-not-lg{
    float: left;
}
@media (max-width: 767px) {    
    .pull-right-not-xs, .pull-left-not-xs{
        float: none;
    }
    .pull-right-xs {
        float: right;
    }
    .pull-left-xs {
        float: left;
    }
}
@media (min-width: 768px) and (max-width: 991px) {
    .pull-right-not-sm, .pull-left-not-sm{
        float: none;
    }
    .pull-right-sm {
        float: right;
    }
    .pull-left-sm {
        float: left;
    }
}
@media (min-width: 992px) and (max-width: 1199px) {
    .pull-right-not-md, .pull-left-not-md{
        float: none;
    }
    .pull-right-md {
        float: right;
    }
    .pull-left-md {
        float: left;
    }
}
@media (min-width: 1200px) {
    .pull-right-not-lg, .pull-left-not-lg{
        float: none;
    }
    .pull-right-lg {
        float: right;
    }
    .pull-left-lg {
        float: left;
    }
}

There is no need to create your own class with media queries. Bootstrap 3 already has float ordering for media breakpoints under Column Ordering: http://getbootstrap.com/css/#grid-column-ordering

The syntax for the class is col-<#grid-size>-(push|pull)-<#cols> where <#grid-size> is xs, sm, md or lg and <#cols> is how far you want the column to move for that grid size. Push or pull is left or right of course.

I use it all the time so I know it works well.

You could put "element 2" in a smaller column (ie: col-2) and then use push on larger screens only:

<div class="row">
    <div class="col-lg-6 col-xs-6">elements 1</div>
    <div class="col-lg-6 col-xs-6">
      <div class="row">
       <div class="col-lg-2 col-lg-push-10 col-md-2 col-md-push-0 col-sm-2 col-sm-push-0 col-xs-2 col-xs-push-0">
         <div class="pull-right">elements 2</div>
       </div>
      </div>
    </div>
</div>

Demo: http://bootply.com/88095

Another option is to override the float of .pull-right using a @media query..

@media (max-width: 1200px) {
    .row .col-lg-6 > .pull-right {
        float: none !important;
    }
}

Lastly, another option is to create your own .pull-right-lg CSS class..

@media (min-width: 1200px) {
    .pull-right-lg {
        float: right;
    }
}

UPDATE

Bootstrap 4 includes responsive floats, so in this case you'd just use float-lg-right.
No extra CSS is needed.

Bootstrap 4 Demo