Yes. You can create up to 500 Recovery Services vaults, per supported region of Azure Backup, per subscription. If you need additional vaults, create an additional subscription.

You can protect up to 2000 data sources/items across all workloads (IaaS VM, SQL, AFS, etc.) in a vault. For example, if you've already protected 500 VMs and 400 Azure Files shares in the vault, you can only protect up to 1100 SQL databases in it.

There is no limit on the number of recoveries from Azure Backup.

Yes.

You can back up Windows Server or Windows machines up to three times a day. You can set the scheduling policy to daily or weekly schedules.
          * You can back up DPM up to twice a day.              * You can set the scheduling policy to daily, weekly, monthly, and yearly.
          * You back up Azure VMs once a day.

Data backed up from Azure Backup Agent, DPM, and Azure Backup Server is compressed and encrypted before being transferred. With compression and encryption are applied, the data in the vault is 30-40% smaller.

No. Backup data stored in a vault can't be moved to a different vault.

No. All data that was transferred into the vault before the backup job was canceled remains in the vault.

          * Azure Backup uses a checkpoint mechanism to occasionally add checkpoints to the backup data during the backup.
          * Because there are checkpoints in the backup data, the next backup process can validate the integrity of the files.
          * The next backup job will be incremental to the data previously backed up. Incremental backups only transfer new or changed data, which equates to better utilization of bandwidth.

If you cancel a backup job for an Azure VM, any transferred data is ignored. The next backup job transfers incremental data from the last successful backup job.