y'all

One of my more treasured roles in life is explaining Americana to immigrants.

And when I encountered "ya all" in written communication, a broad discussion of nonstandard English broke out. The kind of English not taught in English classes where English is not the daily language.

Dictionary.com has an excellent discussion on the use of "you-all", and it's contraction, y'all.

Quick before you look:
1. Is you-all grammatically correct?
2. Can y'all ever be used as singular, a replacement for the singular you?