Blowin in the wind

I was playing this Dylan song “Blowin in the wind” a while ago chord melody style
aaa.pdf (251.2 KB)
very well and now i want to play it again and i forgot it. Is the G chord played on the 10th fret of the A string and is the C chord played on the10th fret of the D string or the 8th fret of the low E string? In this song sheet I added it says its in the key of D on the 7th fret (does that mean you are taking a G chord and moving it up 7 semi tones and you are using the same G chord shape but now the pitch of the G is a D pitch so it changes it from the key of G to the key of D? why would they change this song from the key of G to the key of D? Let me know Thanks
I added a pdf to this post, it shows all the melody notes.

I’m not familiar with chord melody style, but I do play some guitar, so maybe able to address some of your questions.

The pdf you posted appears to be in the key of G, coming to rest on the G chord at the end of the chorus.

I guess where you put the chords on the fret board is up to you, lots of different voicings for the same chord exist, you choose which ever sounds best and is easily reachable. On a standard tuned guitar the positions of the G and D notes are where you stated, G on 10th fret of A string, C on 10th fret of D string and on 8th fret of E string.

Not sure if any of that will be useful.