I think it depends on the Embassy. I have delayed my interview from February 2015 to November 2019 in Kyiv. I just had to email embassy every 6 month to keep my case alive.
you have to contact the embassy that you want to use, explain them situation and ask if they agree tontake the other oarent case. After that write an email to NVC requesting embassy change
Filed for my father on 12/03/2023, application approved in 5 days. It wasn’t expedite but probably because my father is citizen of Ukraine. Today received case and invoice number from NVC