If you have a valid license you just need to send an email to our sales team at firstname.lastname@example.org
and request the older 2015.3.408 Telerik UI version. They will add it to your account and you will be able to download it.
Do you want to have your say when we set our development plans?
Do you want to know when a feature you care about is added or when a bug fixed?
Telerik Feedback Portal
and vote to affect the priority of the items