- Not clear what your question is here
- Backups can only be restored to the exact same appliance model (assuming we’re talking about a backup taken from Gaia WebUI or clish).
- Yes, you can connect your new gateway to your existing appliance.
To elaborate more on the second point, most of the configuration is on the management.
The network interface, routes, etc configuration are part of Gaia OS, which can be replicated with the output of “show configuration” from the existing appliance and applied (possibly with some modification) to the new one.