DrYidd
“YK can never occur on friday because of lo adu rosh.”
Technically its the opposite, lo adu rosh So that YK wont fall on a Friday (ie the “d Wednesday” of adu) but the gist of your post is correct.
MA
What confuses me most about your post isnt the fact that we do in fact occasionally fast on Friday and never push a fast that falls on Friday early fine, you forgot hat we did a few years ago, ITs that why would you argue on the MAgen Avraham?
You quoted the M”A and said it was against halacha?