Answer

General info on channels 12 and 13:

In some parts of the world the use of channels 12 and 13 is not allowed, the most notable region being North American. Smartphones and tablets can determine their location based on information such as GPS or cellular carrier ID to know whether they can connect to APs using those channels.

The WF121 doesn't have access to such information so the only way to know if it's in a region where those channels are allowed is through the country information contained the APs advertising beacon as described in the IEEE 802.11d-2001 amendment. Please note that including the country information in the beacon is optional for the AP.

A1: The WF121 can connect to an AP using channels 12 or 13 if there is any beacon in the scan results which contains country information allowing the use of those channels.

A2: Before using channels 12 and 13 the WF121 must know whether it is allowed to do so. For that reason it is required to do a scan (sme_start_scan) which shows that there is at least one AP allowing the use of those channels. When that condition is fulfilled the sme_start_ap_mode command can be called with channels 12 or 13 in the channel parameter.