#2
Im not sure if this is the way he plays it but these are the chords to the song with a capo on the fith fret.
Intro: G Em Am7 D7

G Em Bm G C Am7 G G7
Somewhere over the rainbow, way up high,
C Am G Em Am7 D7 G Am7 D7
There's a land that I heard of once in a lullaby.
G Em Bm G C Am7 G G7
Somewhere over the rainbow, skies are blue.
C Am G Em Am7
And the dreams that you dare to dream
D7 G Am7 D7
Really do come true.

G
Someday I'll wish upon a star
Am7 D7 G/e Am7 D7
And wake up where the clouds are far behind me.
G F#7
Where troubles melt like lemon drops, away above the chimney tops.
Bm D Am7 D7
That's where you'll find me.

G Em Bm G C Am7 G G7
Somewhere, over the rainbow, bluebirds fly.
C Am G Em
Birds fly over the rainbow,
Am7 D7 G Am7 D7
Why then - oh, why can't I?
G Am7
If happy little bluebirds fly beyond the rainbow,
D7 G
Why, oh, why can't I?

Hope that helps.
#3
I think it's in Eb. Not 100% sure though.
Only play what you hear. If you don’t hear anything, don’t play anything.
-Chick Corea