VPS backup and restore over Internet using VPN

I have a few remote VPS’s (Windows and Linux) that I’d like to backup to my LAN where the UrBackup server is installed. The VPS’s are all KVM. I’d prefer that the UrBackup clients use a VPN so that I do not have to expose the UrBackup server to the WAN.

I have no experience with backing up/restoring remote VPS images so I don’t even know if this is doable. So my questions are:

  1. Since my VPS’s are lone servers, I do not have “site” access so I cannot setup a site-to-site VPN connection. I’ve read that VPN clients are one-way, unlike site-to-site VPN connections which are both-ways. Is a site-to-site VPN required for UrBackup to work properly?
  2. How can one restore a backed up image onto a VPS via a VPN? If you have to use the UrBackup boot disc, how can you also connect to the UrBackup server via VPN if a VPN client is not built into the UrBackup boot disc image? Can the OpenVPN client be installed while the VPS is booted with the UrBackup recovery boot disc? Unless I’m mistaken, you can only install small packages because you’re limited by the amount of RAM on the VPS. Some of my VPS’s have a very small amount of RAM so I may not be able to install a VPN client once booted on the UrBackup boot disc.
  3. Since my VPS’s are with different providers, can the images be restored onto any provider or will they only work on the same server? In other words, can a bare metal restore be performed on dissimilar hardware like you can do with Macrium Reflect’s ReDeploy?