lg optimus one - Why my phone battery has four terminal? what is the use of the fourth?

I have a LG Optimus One (P500). For sometime I am wondering why my phone's battery has four terminals. I am aware that two terminals are for the positive and negative points and the the third connects to the battery's internal thermistor to monitor its temperature. Still that leaves me puzzled with what the fourth terminal could be for?

Interestingly my phone has only three terminal where as the battery has four. I have searched for answers in Google but no useful results other than description about temperature monitoring comes up.

Also since another doubt also lies in the same image, what is the port that is marked as "A" in the following image? It appears to me as some sort connector and my guess is that it is a connector to a cable with which manufacturers can access something deep in hardware. The Nokia phones which I had also had this feature and I guess this should be common for all phone then.

Update: I am more keen on knowing what the fourth terminal on the battery does rather than why there are three in phone and four in battery. As @Axeman said, this battery could be used in other phones (of LG) as well.

Answer

As @Axeman said, the connector is an Ultra Small Surface Mount Coaxial connector (quite a mouthful and still could not get how it was abbreviated as U.FL) which is a kind of expansion port which could be used for any radio communication, including GSM, WiFi, GPS.

And as @Lie Ryan said, the fourth terminal in the battery is for connecting the antennae in the battery to NFC circuitry on the motherboard. Few searches in Google confirmed this and gives raise to following information:

Those who have NFC in their phones, may lose the NFC capabilities if they try to replace with cheap and duplicate batteries which may not have the NFC antennae as said here.

I am summing up all the points to make this question as answered. I was unable to accept @Axeman's answer as complete as it did not answer the NFC part and @Lie Ryan had added as a comment only.

Kudos for them both!

Update: I happen to get hold of LG P500's service manual which confirms the RF connector with the following image tagged as SW1001.