How to know if AirPods are real?

So I had a birthday recently, and was gifted a pair of AirPod Pros. I’ve already owned a pair but sadly misplaced them a summer or two ago, keep this in mind. I’ve been using these AirPods for about a month now, and i’ve noticed a lot of strange things. At first, they seemed so authentic. Immediately after connecting the bluetooth, the 3D pop up appeared on my phone, just like normal, and the connect button was there. Like any regular AirPods (I also purchased the IPhone 16 in the same day) So these seem pretty real so far. But there are a number of things that just don’t make sense, and issues i’ve never had with my old pair. They are BOTH the second gen by the way!

1. The AirPods make sounds I have never heard before. For example, the low battery sound does not make the same noise as it did before, I even looked up the sound effects on youtube. It makes this weird beeping noise that plays about every minute or so, which is not how my original airpods worked. It is very annoying, and that was my first sign that they were potentially fake. They DO however make the connect and disconnect sound like normal, but also makes a different sound sometimes when I put them in my ears.
2. They show up in the Apple Support app, and i found myself testing the repair services to see if the options would show up. While they do show up as My name’s Airpod Pros, I am unable to choose any of the services, as it’ll say “Unable to load Service Option: We’re sorry, this product is not supported for service” Which I find odd, since they show up and register like real AirPods. But my old AirPods will show up just fine.
3. This is the biggest red flag in my opinion. The serial number seems faulty, and when I try to check my coverage for the AirPods, I get all kinds of messages. I’ll try to include as many screenshots as I can, as it’s difficult for me to word some of this. But one being “We're sorry, but this is a serial number for a product that has been replaced. Please check your information and try again. If your information is correct, you may need to contact us.” On top of that, my coverage was expired as SOON as I got the AirPods. They were purchased in December of last year, and I’m pretty sure the limited warranty is a year, so it makes no sense.
4. It makes this ANNOYING mechanical sound when music is not playing!! It’s a high pitched noise that sounds like it may be trying to yk, work? I’m not sure if that makes sense. But it will stop and go, and I’ve never heard this sound before on my old AirPods. It is extremely quiet as well, but just noticeable enough to annoy you.
5. They literally fell apart, and snapped right back on. I investigated on youtube a little and found a woman forcefully deconstructing a pair of AirPod Pros, and the inside of mine look nothing like that. I’m hoping a tech expert can tell me if the inside looks authentic or not.
6. I’m not sure if this is just a feature, but when I turn the volume down to the second to last quietest setting, everything will just go silent, even though my phone is not turned all the way down. I’m not sure if this was on my previous AirPods, but I felt like I should mention.
7. The charging sound is a bit louder, which when I get home I’ll insert a video showing the difference between the old case and new case charging sound.

I’ve included as much of the cons as I have caught so far, but there are some pros. For instance, noise cancellation, transparency mode, and adaptive mode are all present and work as they should, along with the physical buttons on the AirPods. Turning up the volume, pausing, skipping, etc, it all works just fine. Everything else is normal except for the things listed. I’m sorry for yapping but I just really need help! Please someone tell me what to do.

Edit: I forgot to mention these were bought secondhand, which now that I think about it these are most likely fake. :(