Is it true that if someone is from LE, they will not want to show me a picture ID?
And is it true that they do not ever work alone? (I've heard that they would always be in close communication with at least one partner.)

Nothing on their DL states their occupation. They can and have used their real names.

As far as I know, they always have backup somewhere nearby. You might not see or notice them, but they're there.