Unable to make Rest calls in trial version

So I'm aware that Passing appKey in the url is deprecated in thingworx 8 onwards but i still have an option to enable that in platform subsystem. The problem is when i try to that in cloud version it's showing no permission to do that and when i try to set it up in Tomcat server it's not starting because i need a license file for that and for which i need to upgrade my account.
So please help me with this we're a startup. Also alternate methods would be appreciated.