how to interchange position of two divs on mobile

Yes, you can do it.

You need to create a class with the following code:

/*interchangeDiv locationCSS below 768px*/
@media only screen and (max-width: 767px) {
  .col-interchange-12 {
    display: flex;
    flex-direction: column-reverse;
  }
}

and your HTML must be like this

<div class="col-interchange-12">
       <div class="col-lg-8 col-md-8 col-sm-8 col-xs-12"  id="div1" style="margin-top:15px"> 
           @{ Html.RenderPartial("_RelatedInformationLeftsection", Model);}
           
       </div>
       <div class="col-lg-4 col-md-4 col-sm-4 col-xs-12"  id="div2" style="border-left:1px solid #eeeeee;margin-top:15px">
           @{ Html.RenderPartial("_RelatedInformationRightsection", Model);}
           
       </div>
      </div>

that's it, you can check it, below 768px, div2 would be above div1

Swap div positions on mobile using CSS media query, use below CSS 

@media (max-width: 600px) {
  
.container {
  display:flex;
  flex-direction: column-reverse;
}

.section1,
.section2 {
  height: auto;
}
}

Here is fiddle example: https://jsfiddle.net/y4a1fo92/

Thanks