Looks like a misaligned screen protector

There’s no benefit to removing FaceID. It works so quickly that you barely notice it.

• Change your password.
• Enable FaceID.
• Enable auto lock and set to 1 minute.

If the Watch is brand new, it’s almost certainly running WatchOS 10 and will require an iPhone running iOS 17 for pairing.

If the Watch is used, ask whomever you got it from what version of WatchOS it is running.

Most likely you’ll need to update/replace or phone with one capable of running iOS 17 or return the Watch.

With the help of a saw, that arm can easily be removed.

Where should we start cutting? Elbow? Shoulder?

All Apple Watches, to the best of my knowledge, have this ability. It’s a part of WatchOS.