Basic newbie questions about setting up an RB411/R52n-M as a WiFi card in a desktop computer at home.

GOAL:
I would like to ask some basic newbie questions about setting up an RB411/R52n-M as a temporary WiFi card in a desktop computer at home.
1. What is the difference between the pigtail on the RB411/R52n-M being on the LEFT versus RIGHT connector?
2. Why does the antenna seem to be set up for 2.4GHz but the radio will only "see" my 5 GHz access points?
3. Both PTP and CPE seem to work; so which setting is the one I should use for this application, and why?
And, most important:
0. What do I need to do to get the setup to be for 2.4GHz and not for 5GHz?


SITUATION:
I have borrowed a Windows desktop for a few months from a friend who went to Europe where the desktop doesn't have a WiFi card so I figured I'd use a spare RB411/R52n-M as a temporary "wifi adapter" while I am using the desktop. My SOHO Wi-Fi router at 192.168.1.1 is a typical Netgear n router, with both 2.4GHz and 5GHz access points, where it's about 30 or 40 feet away through a few walls so the 5GHz signal strength at the computer is only about -75dBm to about -85dBm (although the S/N is about 35dB).
I'd like to use 2.4 GHz because it penetrates walls better (or so I'm told).
Of course I tried the obvious thing, which is I moved the pigtail from the LEFT side of the RB411/R52n-M to the RIGHT; but when I did that, nothing works. It only works in the LEFT side. So I don't know how to get the radio to be 2.4GHz and not 5GHz and even so, the antenna seems fixed at 2.4GHz (according to the label on the antenna anyway).

QUESTIONS:
This is what my RB411 routerboard and 2.4GHz (I think) antenna looks like (it was given to me for free by a neighbor who changed WISPs)

My first question is what is the difference between when the antenna is connected to the LEFT RB411/R52n-M pigtail connector (as shown here)?
Please note that all the handwriting is mine, and it could be wrong, as it's just a guess, and for the connectors on the left and right, I think it is wrong - so disregard the handwriting on the box!

Versus when the antenna is connected to the RIGHT RB411/R52n-M pigtail connector?

The reason I ask is I'm confused in that the ANTENNA seems to be set for 2.4GHz as far as I can read on the label.
And there doesn't seem to be any setting for the antenna to be 5GHz anyway, even though there must be a way to get the R52n-M card to output 5GHz, isn't there?

Even though the antenna I inherited from my neighbor seems to be labeled for 2.4GHz, the Winbox software seems to indicate it's 5GHz and not 2.4GHz because the only access points it sees in "CPE" setting are my 5GHz access points (and not my 2.4 GHz access points).

My other question is whether I should use PTP or CPE settings for the purpose of using the radio & antenna as a WiFi card in the desktop computer?


So, in summary, I have three newbie basic questions that I would like advice on please.
1. What is the difference between the pigtail on the RB411/R52n-M being on the LEFT versus RIGHT connector?
2. Why does the antenna seem to be set up for 2.4GHz but the radio will only "see" my 5 GHz access points?
3. Both PTP and CPE seem to work; so which setting is the one I should use for this application, and why?

And, most important:
0. What do I need to do to get the setup to be for 2.4GHz and not for 5GHz?

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