You might have to reach out to your Sales Rep to get a trial license for older versions unless someone else comes up with another approach.
As far as I know, those free trials are only available for the latest releases.
Thanks for your response.
7.0 free trail license is disabled when trying to import from 6.5.
I have installed 7.0 however now I am not able to launch dynatrace client 7.0 is it a known issue in windows 10 , I have only one jave version java 1.8.0_144.