Does WiFi Router/AP change the working channel automatically during the normal use? I'm sure a lot of AP or WiFi modem/router can perform an autoscan to select the best channel to be used during the boot. Is the channel selection also performed in other situations (other than device boot)?

This is not a general truth, but some WiFi Routers/ AP's do change the channel without rebooting. Some reasons include, but not limit to:

* Noisy environment on specific channel
* Lots of other AP's on the same channel
* Interference with Bluetooth and/or other RF Communication
* Intrusion Prevention/Detection Systems trigger such as routers sensing that the WPS PIN is being bruteforced by Reaver or other tools
* Another AP with the same ESSID (name) on that channel



Please note that this behavior is very manufacturer specific / firmware specific, for example some Open Source Firmware such as OpenWRT or DD-WRT can be configured to hop channels based on user defined conditions