Hi Sachin,
I have tested the tab auto-complete feature in a Cloud SDK version as far as v131.0.0 and was unable to use it as described. Would it be possible for you to indicate a SDK version in which it can be to reproduce?
Also, I have noticed that a tab auto-complete feature is possible in the latest versions of the SDK as long as the autocompleted bucket was previously used in an another Shell command. Would it be possible that you are referencing to this feature? In that case, you should be able to re-enable the auto-complete feature by running a command with one of your buckets and then run the same command with the same bucket but using the key tab to complete the bucket's name.