#3
Well, when theres a chord with a / like that, it means to play the chord with the note after the / on the bottom. Since there is already an A in an F chord then you just play an F chord with an A note as the lowest note in the chord.
#4
Some examples:

E|-1-    -1-
B|-1-    -1-
G|-2- or -2-
D|-3-    -x-
A|-0-    -x-
E|-x-    -x-
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