Unnatural uses codes which works fine. For just an unlock on a second playthrough do this.
*create password “”
*create unlock false
Add an option to enter a password at the start of the game.
*choice
#password
*input_text password
*if (password = “second”)
*set unlock true
*goto chapter_one
*else
Wrong password.
*goto chapter_one
Then for any choice you want to be specific to a second playthrough just use
*if (unlock)
#special option.
Then add a password at the end of your game
Congratulations on finishing the game, next time you can use the password “second” to unlock new content.
Hope this helps.