@Rekhawar, Nilakshi (Corporate, IND) Thank you for reaching out to us, As I understand you are looking use ARM template to update nbf and exp parameters of existing key.
As per the documentation which you shared - https://learn.microsoft.com/en-us/azure/key-vault/keys/quick-create-template?tabs=CLI in the same doc its clearly mentioned
It's only possible to create new keys. It isn't possible to update existing keys, nor create new versions of existing keys.
Let me know if you have any further questions, feel free to post back.
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