There is a difference between communicating with angels/ praying to God and summoning the dead.
That latter is forbidden. The first two are legit.
As for Joan, she thought she was receiving revelation, but she wasn't.
She was wrong. I find her an admirable figure, but she did not receive special revelation from any angel. That is not Biblical for this age.
What do you mean by this? According to her own testimony, she received constant guidance from St. Michael, St. Beatrice and St. Margaret.
Correct. Remember how King Saul, after falling out of God's favor following his usurping of Samuel's authority as High Priest and the Amalekite incident, contacted the witch of En-dor to contact "Samuel." That was a no-no.