YOu can load specific UI5 version via bootstrap
<script id="sap-ui-bootstrap" type="text/javascript" src="https://sapui5.hana.ondemand.com/1.28.8/resources/sap-ui-core.js" data-sap-ui-theme="sap_bluecrystal" data-sap-ui-libs="sap.m"></script>
What is your Netweaver Version ?
-Vijay