Well, we sync things from time to time, so your account likely already exists there.

yes, it does: https://admin.stg.fedoraproject.org/accounts/user/view/sinnykumari

So, there's on thing we cannot sync (for technical reasons): the ipa/kerberos info. In order to get a kerberos ticket in staging, we need to clear the bit in your account that says it's created (pulled over from prod) and then you need to go to https://admin.stg.fedoraproject.org/accounts login and then change your password (NOTE: do not use the 'forgot password' feature, instead use the change password option).

Once you have done that, kinit yourusername@STG.FEDORAPROJECT.ORG should work and you can use stg-koji in staging. I have added image permissions for you there.

Thanks @kevin , I can successfully do kinit on staging instance and have changed password for my staging FAS account.

I am not sure if I got image building permission on staging because it still says image permission required when I ran

$ stg-koji --profile=koji image-build --config=PATH/qcow2-raw-xz_Fedora-AtomicHost_x86_64.cfg --scratch
ActionNotAllowed: image permission required

Note that --profile=koji overrides the profile provided by stg-koji, so you're back to using production koji.
Please remove the --profile=koji and it should work.

Thanks @puiterwijk , after removing --profile=koji option image-build works fine in stg-koji