Installation: Adding a new Satellite

1) Have RBR50 in AP mode with two satellites (all 3 are on Firmware 2.1.2.18).  System seemed stable/reliable enough that I'm going to add a third satellite that I bought on Amazon.  Clearly the third satellite won't be on 2.1.2.18.  My understanding is that the router firmware can't be more current that the satellite.  Do I have to factory reset all orbis that are on 2.1.2.18 before trying to add the new orbi?

2) I gave my RBR50 a static IP (192.168.1.53).  My two satellites are non-statc but seem to always be 192.168.106 & 192.168.107.  Is there a way to make the two satellites static (and the 3rd static once I get it installed)?  I would like 192.168.54 & 192.168.55 & 192.168.56