I am using < !--nextpage--> to break my posts on multiple pages. This is working fine. But i want to further change the page numbering.

If you visit this post you will noting the page breaks. I want to change the first page to "Question" while the second page to "Answer"

I went through the codex on this page any tried following code on my theme function.php but it broke my site.

<?php wp_link_pages('before=To read this story, &after=. &next_or_number=next
&previouspagelink=you can go back to the previous page
&nextpagelink= or you can read on to the next page'); ?>

Could you please help to get the right code. I do not want to keep more than two pages, if this helps. And if someone can help me to get the shortcode for < !--nextpage--> it will be cherry on top of ice cream :)