U103 – How do I keep students from viewing the questions after they've submitted?
Set a custom password for "General > Correction and scoring options > Submit/show answers password".
When a student submits their answers for a widget, their widget view will go into a so-called check state. This is the state were, in case the widget is configured as such, correct answers and your rationales are displayed, and in which the student can no longer make any edits.
In a Quiz, Video Quiz, Worksheet or Split Worksheet widget, you can protect this state with a password. This means that before students end up in the check state, they have to provide the password.
There is a ingenuous trick you can perform with this password. If you have configured one, and a student that has just submitted their answers receives the pop-up window that requests the password, the background goes blank. This means that as long as the pop-up is on screen, students won't see the widget questions nor their own answers. And if they haven't been provided the password, they won't be able to advance either.
You can use this technique for tests: if you want the questions to disappear as soon as a student submits, for example because you want to avoid them taking screenshots that they could send to peers, protect the widget with a Submit/show answers password that you don't share with students.