For backup, the recommendation is to use FTP/SFTP as per vShield Install Guide / Admin Guide https://www.vmware.com/support/pubs/vshield_pubs.html
For password, you can reset the admin password from the vCNS Manager web interface with below steps:
1. Log into the vCNS web interface.
2. At “View:” in the left corner, select Edges.
3. Select the Edge Gateway you want to log into.
4. Click Actions and select Change CLI Credentials.
Bayu Wibowo | VCIX6-DCV/NV
Author of VMware NSX Cookbook http://bit.ly/NSXCookbook
https://github.com/bayupw/PowerNSX-Scripts
https://nz.linkedin.com/in/bayupw | twitter @bayupw