RED migration and failover question

Question

I've only set up a RED 15 so far. I need to migrate it from an XG210 to an XG310. Here are my questions: 
 1. I understand the 2nd firewall IP/hostname in the RED settings is meant for failover or loadbalancing to the same XG firewall. But i wonder if I could use it in my case -- put in the WAN IP of my XG310 as the 2nd IP in the XG210 RED settings and set up the same RED settings on my XG310, so that when I disable the RED interface on the XG210 the RED will failover to the XG310. 
 2. If the above won't work, can I simply configure a new RED interface on the XG310 with the unlock code and disable the RED interface on the XG210, then the RED will be forced to download the new configuration from the Sophos provision server and join the XG310 automatically? 
 3. After I migrated the RED to the XG310, if i have a need to change the firewall's public WAN ip again, can I simply update the RED settings with the new firewall IP first and then proceed to apply the new IP on the WAN interface? I guess if updating the RED settings works this way, it doesn't matter whether I enable the new WAN ip afterward or beforehand, correct? 
 
 Thank you very much!

2ServeErik · Accepted Answer

Hi Daniel, 
 1. Interesting idea... but it won't work. A RED can only connect to one XG, hence its unlock code. 
 2. Yes, this is how it's designed to work. You can disable or even delete the old RED interface on the XG210. 
 3. Yes and correct. However, you could also use a hostname (for example "XG310.mydomain.com") instead of a public IP, and change your public IP in DNS. 
 Good luck.