#1
is there a difference between the blues and pentatonic blues scales?
#4
No, there is no difference between them. The blues scale is just short for the pentatonic blues scale (an incorrect name btw.. The blues scale is hexatonic )
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#6
Pentatonic: Any 5 note scale, though us guitarists generally use it to mean the minor pentatonic scale. The minor pentatonic is the natural minor scale without the 2nd or 6th (in creation at least, not really in use).

Blues Scale: A 6 note scale that-minor pentatonic with the note between the 4th and 5th added. This is a b5 and it gives a bluesy sound, hence the scale's name.