FCC vs CE mode

How does the air unit communicate with Herelink?

“Up to 20KM in FCC mode and 12KM in CE mode” What’s the difference between these two modes?

Why does Herelink have a SIM card slot?

They are communicating on 2.4GHz ISM.
https://docs.cubepilot.org/user-guides/herelink/herelink-overview#technical-specifications

The power determines its maximum range. When you select the region, it automatically fit the local RF regulation.

No.

How is it possible to have 20km range on 2.4GHZ? That’s the same as a router, and I have never seen a router with 20km range.

It does have a SIM card slot, and the antennas even have a label with “wifi” written on them

Using the same frequency band isn’t necessary mean using the same technology.
The Herelink uses 2.4GHz ISM, and it does interfere with Wifi signals, but it is not using Wifi. It is not a router.
You can find videos on Youtube about people testing Herelink’s maximum range.

Herelink don’t have SIM card slot. It is a SD card slot.