I read through several threads and I wanted to confirm the following:

Booked using AC miles at the lower saver level
IAD-GRU (UNITED POLARIS)
GRU-EZE (AC ECONOMY)

Although I am happy with the value of 80+ percent business class, I am wondering if availability for the AC segment opens up in J, Or even PE, Does the ticket require both $100 change fee and the potential miles price difference too?