EDIT: This topic is obsolete, since Nicec00lkidd forcefully updated YBBR to version 1.1.2, hopefully fixing this issue.
For those of you who started playing on version 1.1.1 and didn't unlock extras, there is a bug where completing a bossfight and going back home does not unlock extra modes and the credits tab in options.
You need to obtain an older version of YBBR from GameBanana, complete the bossfight, and upgrade back to version 1.1.1.