Hi Devanand,
Yes, you can selectively expose your Client 20 to the SAP GTS services through appropriate settings in the ALE distribution area itself. Basically, you will define Logical system name for each client and then these logical system names can be specifically be used as a bridge to consume the SAP GTS services.
I hope you got it now.
For any further queries, please let me know it.
Regards,
Aman