Hello Jitendra,
As per you posting ,I had created app same like com.test.dept and added gateway user ID and PWD in backend and added security profile...
After that I am able register my created App using Rest Client Connection URL and able fetch data of gateway service..
Attaching screen :
But same service not able to fetch data from ODATA SERVICE of SMP , It looks like i am not giving correct URL in destination or might be i did not understood it.
Yes i raised ticket for OSS, today. Waiting for basis team to confirm 
.
Kindly guide..
Regards
Vivek