Hello, how are you?

1. When you have to restore NSX-T, be sure to deploy a new appliance with the same IP and Hostname (FQDN), as also in the same version as the old one. It not necessary to do anything else. Just deploy and point to the SFTP server with the right configurations.

2. When you backup NSX, all configurations will be written in the backup file. What you do after the backup obviously doesn't count. That's why it's interesting to backup periodically.

3. You can delete the old files directly in the SFTP server, but, check this doc: https://docs.vmware.com/en/VMware-NSX-T-Data-Center/3.2/administration/GUID-ECFFBD6D-4D2F-4773-B552-...