bind8 and bind9 compatibility

[Roman Mashak]

Hello,

I have some application using API from Bind-8.2.3-rel (basically it
uses some Dynamic DNS functions). We're planning to upgrade 8.2.3-rel
to bind9. Hence two questions:

1) what bind9 stable version you recommend
2) what kind of compatibility problems we can expect
3) should we rewrite our application with use of new library API?

Thanks for help.

--
Roman