Sorry to hear that. I wish there was more I could do to help. Complaining on Reddit won’t change the reality of smart device theft. You’re in general shit out of luck. Next step if you haven’t already is purchasing a new phone. You’re not “punishing anyone” by locking the phone as in a worst case the screen and other parts can be sold second hand to small repair shops.

You can request it but there are no guarantees it’ll go through. Often it gets removed from your account and EIPs removed. You could try to mark it as stolen again, but it will just get unlocked again. The device is lost, this is why insurance exists, file a claim and buy a new device.

The IMEI does not get changed. The carrier removes the stolen flag from from the cross-carrier database.

As I said, previously, rogue employees at AT&T and other cellular providers, go into the database and remove the stolen flag, as well as any equipment installment plans. Using the services is funding organized crime. However, this is why you should purchase AppleCare or similar so your stolen device can be replaced without paying another thousand dollars.

Yes IMEI unlock services are run by rogue cellular employees so they have access to the backend and abuse their access to make a few tax free bucks.