My RB2011 normally acts as a wifi ap and a wired router for my SOHO to my ISP.

Sometimes however my ISP goes down and I would like to be able to load up a config that would use my Android phone's hotspot (SSID 'AndroidAP'; no security) instead of the ISP. That is, become a client of the hotspot and route all wired traffic bound for the internet out through the hotspot.

The RB2011 only uses 3 interfaces: wlan, ether-1 and ether-2. Ether-1 connects to the ISP equipment, and ether-2 connects to the SOHO switch.

Starting from a factory reset condition, could someone kindly show me what commands to run to get a config like this?

Thank you for your time,
Dave

you can setup virtual interface in wifi. in different mode if you wish and configure(from routing and firewall to deeper things(except wifi hardware options of course separetely for each.

This is difficult because the WiFi cannot be access point and optional client at the same time.
I ran into this recently.  It is no problem to be either AP or Client, and it can be AP and Client at the same time, but not
with the Client not connected all the time.

No real need for the AP to work during fail-over. All of the servers and workstations that truly need internet access during fail-over are wired.

Could be, but that still makes it difficult.
It means that you need to re-configure the Wireless when you have an outage on the fixed line.
That means it has to be done by tricky scripts instead of the normal failover procedures that use metrics and gateway
checks or interface up/down to change the routing.

No need for it to be automatic...  I have no problem running a rsc to set it to fail over and then an rsc to set it back to normal.