Anytime you plug something into a single combo audio jack, the computer should ask you "which device did you plug in".

If your laptop didn't ask you before, it means that you didn't install the correct driver or that you select "never ask me again".

If you plugged in your 3.5mm speakers into the laptop and the speakers were listed separately, it means that you didn't install the correct driver and you are using the microsoft windows generic audio driver.

So it means that for the longest time, you didn't install the correct audio driver, the OS used the windows generic audio driver. Then windows update install the correct audio driver for you.

You also continued to provide useless answers and questions. I put it in bold that if dell gives you a choice of "line out" vs "headphone" --- no answers from you.