Okay

1. It's not the first chord of the SONG, it's an introductory sound played by itself before the song begins. Thus:

BLONG!
rest
"It's been a hard day's night..."

2. The notes are F,G,C and D. To put it simply, somebody's playing an F chord while somebody else is playing a G chord, but they are using the common technique of leaving out the third. They are playing open fifths.

3. They are playing all the above at a low pitch, because high is simply too irritating.

Interesting and effective.