if you're using RC4 - simply follow the update instructions from the Update History
available in our downloads
section. You will find the list of all changed files there.
As from the Update History:
Changes comparision: 2.0 RC6b - 2.0 RC6c Updated files:
* bb_codes.php - URL improvements
* bb_func_vthread.php - SQL improvement
* bb_func_stats.php - faster SQL queries now
* bb_func_txt.php - urlMaker() improvements
* bb_functions.php - version change
* index.php - "Move Permanently" header on moved topics
* setup_mysql.php - removed function getByDay()
templates/tools_edit_post.html - var anonPost=0; added
But you will need to follow all changes not only 2.0 RC6b - 2.0 RC6c, but also 2.0 RC5 - 2.0 RC5a, 2.0 RC5a - 2.0 RC6, 2.0 RC6 - 2.0 RC6a, 2.0 RC6a - 2.0 RC6b and also 2.0 RC4 - 2.0 RC5...
so it's better to simply overwrite all miniBB files you haven't changed with new ones.. and see what changes have been done to files you've modified .. if there're any crucial changes you will need to overwrite these files too and later do all changes you've made to them again..
The older is your board, the harder it's getting to update to the latest version.. so in many cases the simplest way to overwrite all files and then redo all custom changes you've done to it..