Tim Hunt

Part of what you need is in Moodle 4.4: https://docs.moodle.org/404/en/New_for_teachers#Quiz_improvements lets you calculate the score for each group of questions.

MDL-81374 is a feature request to all feedback based on those scores for groups of questions. Maybe in Moodle 5.0.

This did not work until Moodle 4.2.6, 4.3.3, 4.4, but it should work now: MDL-36733.

Does your Moodle site let you use a custom theme? That would let you affect all questions consistently.

Alternatively, you can add extra styling using https://docs.moodle.org/405/en/Header_and_footer

Yes.

In the version.php file for a plugin, you can declare that it requires another plugin. E.g.

$plugin->dependencies = [
'filter_embedquestion' => 2022032900,
'quiz_answersheets' => 2022033000
];

(And the dependency can be two-way if required, e.g. the block and the local plugin both depend on the other one.)

Not sure how similar it is to your needs, but https://github.com/moodleou/moodle-qtype_recordrtc/tree/main/tests/behat might help?