Using an AP1, your pairing options are the basic wildcard search, pairing bit, or using a search list. All of these are explained in detail in the "Device Pairing" application note found in the Devzone. If you have not already registered for the devzone, do so now and then download the application note.
Yes, it will be a first in, first serve pairing with the master -> when the slave channel is opened (say on channel 0) and performs a wildcard search - it will establish a channel with the first matching master. there is no way to know which master it will pair with, unless you pair each in isolation.
Once you have that channel established (channel 0) and open a second channel (channel 1) with the same wildcard search it will not find the master that is associated with channel 0, it will only look for a different matching master. This is handled seamlessly by the ANT protocol.
Once a channel is established you can use a requested response message to obtain the channel ID of the device you are connected to.
You can search for multiple devices and select the one you want -> refer to search lists in the device pairing application note.
