@Hemachandran V Sorry for the inconvenience this must have caused!
According to your description, your Recovery Services vault: “defaultVault403” contains VM backup data for the VM, which prevent you from vault deletion. In order to delete the resource group you need delete all the resources within that resource group, one among them is the vault.
You still can go to Recovery Services vaults->Backup Items->Azure Virtual Machine to check those backup data as Restore points.
Hence, to delete the vault, you need to firstly cleanup all the backup data following the steps below:
Go to Recovery Services vault->Properties->Security Settings->Disable the soft delete feature. Reference: https://learn.microsoft.com/en-us/azure/backup/backup-azure-security-feature-cloud#disabling-soft-delete-using-azure-portal
Go to Recovery Services vault->Backup items->Azure Virtual Machine-> Select the VM that was enabled with backup->Stop backup->Delete backup data
After you completed the steps above, you should be able to delete the Recovery Services vault successfully.
For detailed instruction, please refer to this document: https://learn.microsoft.com/en-us/azure/backup/backup-azure-delete-vault
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