Hey & welcome to GT!

Originally Posted by: bebopinvasion

1) Lets Say i want to play in the Key of C. the Next two major chords are F and G. Do i have to play It in those order C => F => G or can i mix it up like G => C => F.

2) when i mix it up is it still called "Key of C"?

[p]Yes, most likely. And from a beginner perspective that's the best way to look at it.

But you would not know for sure until you know what the melody is. Or what notes were being played over the chords. The voice leading (which specific notes over which specific chords) determine harmonic function & key signature.

In the key of C:

C (I)

F (IV)

G (V)

So as long as all the melody notes are from the C major scale, then you are in C, but the chord progression is:

G (V) / C (I) / F (IV)

But if the melody has a B-flat, then you are using the F major scale (f, g, a, b-flat, c, d, e) & you are in the key of F with a modualtion:

G (II or V of V) / C (V) / F (I)

I have a whole series of tutorials on music theory if you are interested.

https://www.guitartricks.com/collection/music-theory

Hope that helps!