I am trying to shuffle 1st item with 2nd item, 3rd item with 4th item and 5th item with 6th item...and so on.
Condition : Items are not fixed. It can be more than 6.
Existing scenario

Expected Result

I am trying to shuffle 1st item with 2nd item, 3rd item with 4th item and 5th item with 6th item...and so on.
Condition : Items are not fixed. It can be more than 6.
Existing scenario

Expected Result

If your items have the same height (as on your picture), you might shift even items upwards, odd ones downwards, and here you are:
li {
border: solid 1px;
margin: .25em 0;
background: #6df;
}
li:nth-child(odd) {
transform: translateY(calc(100% + .25em));
}
li:nth-child(even) {
transform: translateY(calc(-100% - .25em));
}
<ol>
<li></li>
<li></li>
<li></li>
<li></li>
<li></li>
<li></li>
<li></li>
<li></li>
</ol>