#3
Guitar scales isn't the thing to ask.
Any musical scale can be played on a guitar.

There are tons of scales; people make them up.

Some get very popular like the pentatonic.
#5
There are only 266 heptatonic scales/modes of these scales that only contain semitonal, tonal and augmented tonal steps. You can thank Aenimus Prime (Andy) for this geniousness.