Backup Exec 22 license downgrade to Backup Exec 20

We are planning to upgrade our existing server infrastructure & Backup Exec 14 and planning to purchase Backup exec22 . However, due to some compatibility issue, we need to deploy Backup Exec 20 for around 3month until other components upgrade completed. 

If we purchase Backup exec22,
does Veritas offer a downgrade option / temp license for installing Backup Exec 20?

thanks.