prc format is the same as mobipocket format (.mobi), as far as Kindle is concerned, so there is no reason Calibre can't change it for you.
According to the Mobipocket Dev center, you can set the start option to where you want the book to open. Have you tried that?
"start: if the "start" type of subitem is present, the action defined in the onclick is performed whenever the ebook is opened. Use this in dictionaries to make the dictionary open on the first page every time instead of the last page read. The last page read is not very useful in a dictionary.
<guide> <reference type="start" title="Start here" href="starthere.html"/> </guide> "
Have you tried mobi2mobi to change metadata? See https://dev.mobileread.com/dist/tomp...mobi2mobi.html
I think you might be forced to create a new copy of the file, anyway, though.