VMware VSPHERE 5 ESSENTIALS KIT FOR 3 HOSTS - questions about licensing

We need to perform incremental backups of an old server running esxi 4.1 free.

1) Can we buy a license of "VMware VSPHERE 5 ESSENTIALS KIT FOR 3 HOSTS" and use the license downgraded to unlock backups?

2) Is "VMware VSPHERE 5 ESSENTIALS KIT FOR 3 HOSTS" what I need to use veeam backup to do incremental backups?

3)This allows me to use the license on three hosts simulatenously?

4) If we buy a new server can I use a downgraded license (to vsphere 4) for the old one and one of the other for the new one supporting vsphere 5)?

5) With this kit can I use vsphere essentials on three hosts at the same time?

Thanks a lot