More about modes.
1) A mode is a varation of a scale you probably already know
it is used to ift over a chord or chords example if you are playing over a G7 chord the G major will conflict with one of the notes in the chord. The G7 chord uses a natural F note Note an F#.
What to do~ Answer You use the mixolydian which contain all the notes of the G major except the F# it is replaced with a F natural
Inclusion you use modes to fit the key I don't think you use the modes to pick out the chords in a key
1 2 3 4 5 6 7 1 (use 1-4-5 off chords 2 & 6minor)
G A B C D E F# G G C D A E minor
P.S Thanks to all for replying I have learned form reading and replying and hope I have shared some useful information