How to disable Arduino Yun to work as Access Point and set it to work as needed?

Hi, I am using Arduino Yun and I would like to disable it to work as Access Point. That is, I don't want that it is displayed in the list of available networks.

Then I would like to set and use it (separately) in the following scenarios:
a) Arduino Yun connected just over a given Wi-Fi network (Ethernet connection disabled).
b) Arduino Yun connected just over Ethernet (Wi-Fi connection disabled).

How can I make it?

Note: In my previous attempts I tried to customize and/or disable someway the Wi-Fi connection (through the LuCI panel) in order to reach what I am looking for but in all of these cases I had to restore my Arduino Yun from scratch because it did not work anymore.

b) Arduino Yun connected just over Ethernet (Wi-Fi connection disabled).

Using the onboard Ethernet

When you connect the Yun to a wired network with an ethernet cable, it will try to connect automatically via DHCP. The board will show up on the ports menu just as it would over WiFi.
If you want to connect the Yun directly to your computer, either configure the computer’s interfaces to have a static IP address, or act as a DHCP server.
NB: the ethernet interface is eth1, not eth0

Disable wifi:

nano /etc/rc.local
#wifi-live-or-reset

a) Arduino Yun connected just over a given Wi-Fi network (Ethernet connection disabled).

follow instruction of “Configuring the onboard WiFi”