iTutor Musics Updates

I finished reading books about music and studying theory and started to examine the songs. I’m examining Sweet Child O’ Mine by Guns N’ Roses. I found a text which explains the theory of it on internet. I have some questions about the approach of the text.http://www.guitar-music-theory.com/b...-guitar-solos/ The song is G Major and it switches E minor on final solo. General chord progression is D-C-G-D (V-IV-I-V) Chord progression on the last (third) solo is Em-C-Bmaj7-Am (i-VI-Vmaj7-iv) “While the D-C-G-D progression is drawn from the G major scale, it’s actually the 5th degree, D, that is used as the tonic. In other words, D is the primary chord and where the music begins and ends. When the 5th degree of the major scale is used as the tonic, it’s called Mixolydian mode.”1) Is that considering what chords are primarily used and then decide which scale it is true? Should i examine in this way? “The third solo switches keys to E minor. The chord progression is now Em-C-B7-Am. Em-C-Am fit into the G major scale, but with the music centering on G’s 6th degree, E. This makes E Aeolian mode, better known as the E natural minor scale. You use a combination of E minor pentatonic and G major scale patterns. When the B7 is played, raise the 7th degree in the E minor scale from D to D#. The raised 7th makes the E harmonic minor scale.”2) How did he decide it is E minor? Is the reason behind it is that B maj7 is used and then he relate it with E Harmonic minor because of raised 7th? (B is 3^rd in G major scale and it’s quality is minor) (B is 5^th in E minor scale ad it’s quality is minor) (But it is used as major 7^th)