Hi Mishra,
No, Azure Backup doesn't support backing up VMs across subscriptions to a single Recovery Services vault. Each vault can only back up resources within the same subscription. You'd need to either move VMs to the vault's subscription or use separate vaults per subscription.
More details:
- https://docs.azure.cn/en-us/backup/backup-azure-move-recovery-services-vault
- https://learn.microsoft.com/en-us/answers/questions/1378022/azure-vm-backup
- https://learn.microsoft.com/en-us/answers/questions/1531957/powershell-script-to-take-backup-of-azure-vm-with
If the information helped address your question, please Accept the answer.
Luis