Hi Abhijot,
From the rest client if you are not using a backend url which doesn't need credentials you have to pass your trial account credentials.
ie. smp-p1446543231trial and password.
If the backend url needs authentication you have to pass the backend credentials instead of your SMP trial account.
I have used a rest service as backend url (http://www.thomas-bayer.com/sqlrest/) that doesn't need authentication and it worked.
Regards, Midhun
SAP Customer Experience Group - CEG