If you try to uninstall a question type where you have created questions of that type, you will find that the option does not exist, becuase it would break those questions.
If you deleted the question type plugin manually on the server, then you will find that those questiosn don't work any more (and proably lead to error messages being displayed). HOwever, all the releated data would still be in the database, so if you re-installed the plugin, things would probably start working again.
If you deleted the question type plugin manually on the server, then you will find that those questiosn don't work any more (and proably lead to error messages being displayed). HOwever, all the releated data would still be in the database, so if you re-installed the plugin, things would probably start working again.