how to restore icloud details when someone dies

Please explain what you mean by "restore". Normally you might want temporary access to download photographs or something as provided in this document How to request access to a deceased family member's Apple accounts. After that the procedure is deletion of the ID entirely. hhttps://www.apple.com/legal/internet-services/icloud/en/terms.html

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D. No Right of Survivorship

Unless otherwise required by law, You agree that your Account is non-transferable and that any rights to your Apple ID or Content within your Account terminate upon your death. Upon receipt of a copy of a death certificate your Account may be terminated and all Content within your Account deleted. Contact iCloud Support at https://support.apple.com/icloud for further assistance.